I live in São Paulo and think it is a great city, and Brazil overall has been improving a lot these past few years. But as another poster wrote the negative aspects and exaggerations can be put to good use to provide a cyberpunk flavor. So here's a few select facts for São Paulo, followed by how you could use them in the setting:
the city is very vertical, thousands of buildings but has few really tall ones (ex: Edificio Banespa and Edifcio Italia) -> include a few megahigh-risers but not too many, most buildings should remain within 20 to 30 floors
public transportation is crappy, buses are irregular and the subway is quite nice but has very limited reach -> how about an expanded but always-packed subway system (with both underground and over-the-ground trains)
traffic is horrible -> make it more horrible, a city always stuck on traffic. so how do you get anywhere? well..
SP has the largest helicopter fleet of any city in the world, and most buildings have helipads -> this is how you know if you are rich in future-SP. every family wants to buy their own helicopter.
further, SP has a lot of motorcycles driven mostly delivery boys (called "motoboys") which zig-zag between traffic and lanes at very high speeds (it's not illegal to ride between lanes), to the point that 3 motoboys die every day -> just ramp up the numbers, this would be the high-risk helicopter alternative for the not-so-rich
current airports are always crowded -> make them more so. Congonhas could be a very dangerous airport due to being smack in the middle of the city (see the 2007 TAM accident). Guarulhos and Viracopos are quite far, and don't have that much space to grow either. Maybe in the future there's a new floating airport in the south side - call it Guarapiranga airport and put it smack in the middle of the Guarapiranga Reservoir
more Japanese immigrants live in the city of São Paulo than in any other country in the world -> just drive to Liberdade neighborhood for an Asian flavor. any Japanese Megacorp / Zaibatsu is certain to have a presence in the city
the racial make-up is quite diverse, with a lot of mixing; prejudice tends to be economic rather than racial
Typical day-to-day cuisine is rice-and-beans plus meat and salad, but nice cuisine is generally Italian or Japanese, with hundreds of restaurants -> maybe SP chefs will be the first to come up with an Italian-Japanese fusion cuisine (feel free to imagine how that would work)
Pizza is almost a weekly religion for all social classes, it's dinnertime food only but you can make it at home, go to a regular pizzaria (order on the menu), a rodizio pizzaria (all-you-can-eat, waiters come to your table and say "Mozzarella" and if you want the flavor you ask for a slice) or delivery (called "disk-pizza", from the verb "discar" which means call through the telephone) -> yeah, your characters eat pizza and it can be great prop for your gaming group :)
Many streets in São Paulo have weekly "feiras livres", or open fairs where neighborhood inhabitants purchase fresh fruits and vegetables. The owners move their stands/barracks from feira to feira, depending on the weekday; nowadays most feiras even have pirate DVD stands -> some "feira" could become a front for illegal contacts, software or even biotech; fruits will have a lot of chemicals and toxics
95% of DVDs sold in Brazil are pirate copies, which can be found in any feira or, even better, in the Santa Ifigenia street with dozens of contraband and pirate shops -> SP could be a major hacking-and-cracking hub in your world, particularly if China turns hard on IP rights once it's the largest economy in the world
for nightlife (which happens every night, Monday to Monday), you can go to either a "boteco" (bar) such as Original or and sit down, drink and talk to friends the whole night, or go to the "balada" (nightclubs) such as Lions or Disco with trendy techno music, lights and drugs -> not much change in the future, I'd guess...
prostitution is as common as in any large city, but high-end places such as Club Bahamas and Cafe Photo work like nightclubs + hotels that receive a cut from the prostitutes -> they could expand, maybe even franchise their operating model...
there are plenty of hotels in the city for all social levels; but there are also motels that rent rooms by the hour, where couples go to engage in sex -> seedy motels could be a good place to do business, luxury motels should have huge bathtubs and thematic decorations straight out of Las Vegas
people usually leave their parents' house only after college or sometimes only when getting married, that's why they need motels for occasional sex -> even in the future shouldn't be uncommon to have rich 25-year-olds living comfortably with their rich parents
Brazilian corps are on the rise, merge them and make them more so -> in future SP Itau-Bradesco is the bank of 90% of the population, 95% drink beers such as Skol or Original from InBev, Procter & Johnson owns 80% of your daily products, and Carrefour-de-Açucar is the only supermarket where people buy food and cleaning supplies
most shopping (clothes/jewelry etc) is done in large malls called "shopping centers", from luxury ones such as JK, Iguatemi, Cidade Jardim and Morumbi to mid-level ones such as Shopping D and Interlagos -> continue the trend, and make new ones incorporate residential and commercial areas - so rich people could live, work and shop in the same block, avoiding traffic altogether
Soccer is the popular entertainment of choice, but the largest fan clubs ("torcidas") are quite violent -> they could become true gangs, battling an urban war whenever their teams play: Gavioes da Fiel (the Hawks, black-and-white, numerous and violent) roots for Corinthians, Independente (independents, red-black-and-white, sophisticated sycophants) roots for São Paulo Futebol Clube, Mancha Verde (green spot, green-and-white italian brawlers) roots for Palmeiras. Their stadiums are Itaquera, Morumbi and Parque Antarctica, respectively.
São Paulo had a large prison smack in the middle of the city, called Carandiru -> make it return, a mega-prison with multiple blocks ("pavilhoes") called Carandiru 2. Or maybe just wall-up the whole Carandiru neighborhood, make it an isolated crime region a la Arkham City
the largest gang permeates the prison system, it's called Primeiro Comando da Capital, or PCC, and has actually engaged in violent attacks against the police -> and now you have the reason for abandoning a whole neighborhood to the gangs
the SP-equivalent of BOPE is called ROTA -> just give them better weapons, and that's your police force
violence has been dropping but property crimes still rank high: there are "sequestro relampagos" (lightning kidnapping) in which a criminal kidnaps you, drives you to an ATM, forces you to get as much money as possible and releases you in the same night; there are "arrastoes" where gangs invade residential buildings and recently restaurants and go floor-to-floor or person-to-person getting all their jewelry and belongings -> continue the trend, you never know when a gang will get into your apartment and steal that macguffin you just captured last game
to protect against this many rich people have personal drivers and bodyguards, and there is a very significant fleet of bulletproof cars -> few cars won't be bulletproof in cyberpunk SP, at least against small arms
seasonal activities include nightlights on Avenida Paulista during Christmas, a huge party at the same place on New Year's eve, and "Festa Junina" during June-July, with "quermesses" (fairs) at night on church plazas where people drink warm wine ("quentão") and get warm by the fire -> keep it as is for local flavor
on Carnaval the city is empty! Everyone goes to the beach or the countryside, it's the only time in the year with no traffic (but no nightlife either)
winter is not that cold, but there's a lot of pollution due to thermal inversion. Summertime is quite rainy (in particular March-April), floods can completely stop traffic, and the energy grid can and does blackout often during heavy storms and occasional hailstorms. Summer rains can also bring dengue fever due to still water captured in makeshift recipients -> climate change could make storms heavier and hailstorms more frequent and dangerous. and make seasonal diseases common occurrences: wintertime pollution-related asthma, summertime dengue fevers
due to mild temperatures houses and apartments rarely have air conditioning, and almost no-one has central heating or a fireplace. Commercial buildings do have AC, though
recreation happens mostly in Parque do Ibirapuera, one of the few green places in the city, open to everyone -> make SP heavily polluted, no green, and close Ibirapuera to rich people only
the outskirts of São Paulo offer nice settings too; from forested sierras that drop down to the beach cities of Santos and Guarujá, mountains waterfalls and an English Village of Paranapiacaba at the South side, to the Cantareira forest and Jaraguá peak that overlooks the entire city in the north side, and actual native-Brazilian villages and reservations in some spots, it's all a 60-min drive away (without traffic)
Yes, the city could sustain a large campaign just by itself... But here's a few ideas for other cities: