I'll start by offering a few things that might help you make your own judgement, and clear up some misconceptions you seem to have.
Check the Basic Rules
Although you don't have access to the PHB until it's already time to make the character, a significant portion of the relevant content is available for free in the Basic Rules. They are available in PDF form from the Wizards of the Coast website, or in a more interactive form on D&D Beyond. Either one should be able to help you plan things somewhat in advance, though the specifics of the Eldritch Knight are not included. I'll be linking to pages within the D&D Beyond version whenever I can for this answer.
Spell preparation is changed, but not much
You mention that you heard "Wizards and Clerics no longer have to prepare spells every day", but that is deceptive at best. Some classes don't need to prepare spells, but Wizards and Clerics definitely do. If a prepared caster wants the same spells prepared on consecutive days then they don't strictly require separate preparation, but that particular difference is unlikely to have mechanical consequences. In the sense of "Wizards need to decide in the morning what spells they will cast during the day", that's (mostly) still true.
Useless in combat?
You stated that your reason for not being just a Sorcerer is that you don't want to be "worthless in combat", but Sorcerers don't match that by my description. Sorcerers are certainly fragile, but can be very effective in combat if they avoid getting hit.
What does a Sorcerer with 1 level in Fighter look like?
The biggest thing that a Sorcerer gets from the first Fighter level is enhanced durability. Sorcerers can't use any armor effectively on their own, while a single level in Fighter gives at least medium armor, and depending on some other choices could also give heavy armor, a shield, and/or a flat +1 AC bonus at all times. Single-class Sorcerers can use mage armor and similar spells to make up for the lack of armor, but a Fighter dip will usually give an even better result and leave the extra spell-slot for other spells.
The other feature you get is Second Wind, which heals 1d10 plus fighter level HP refreshing on a short rest. For a low-level character that can be pretty significant, but it drops off quickly if you don't take more Fighter levels.
Other than those added durability options, your character would basically end up as a normal Sorcerer. Cantrips will be more effective than weapons in most if not all situations, and the difference only gets more significant as you level up Sorcerer more. Sorcerer spell progression is slowed by the dip, but you would still be able to reach all spell levels and those spells would be just as potent as a single-class sorcerer.
A second level in Fighter would grant the powerful Action Surge ability to enable the Sorcerer to cast two spells in a single turn. Most of the other Fighter features wouldn't benefit a Sorcerer much, especially not without a much larger number of Fighter levels.
What does an Eldritch Knight look like?
The Sorcerer with a little Fighter ended up being mostly a more durable Sorcerer. An Eldritch Knight is closer to the opposite end, and is a lot like a normal Fighter with some magic options. An Eldritch Knight will always be far behind a Sorcerer in terms of casting powerful spells; Sorcerers get access to higher level spells much earlier, and go all the way to potent 9th level spells, while Eldritch Knights gain spell levels so slowly that they only reach 4th level spells. Those spells aren't bad, but end up a lot closer to a Fighter with a small Wizard dip rather than a Sorcerer with a small Fighter dip.
It's also worth noting that Eldritch Knights use the Wizard spell list, which is significantly different from the Sorcerer's. I haven't gone through the whole thing, but it seems like the Wizard list has a lot of extra utility/control spells.
Eldritch knight is "Fighter with some spells". Sorcerer with a small Fighter multiclass is "Sorcerer with some armor". Either one would probably be fine enough, though the Sorcerer basically won't ever use weapons; if you want the character to be fighting with weapons sometimes then a different option would be better.
A Druid might be closer to the combat role you wanted, though the character concept is very different. Druids can use some armor and more weapons than Sorcerers and have a bit more HP, so they could be about as durable as a Sorcerer/Fighter mix. Druids have full spellcasting progression like Sorcerers, so can reach 9th level spells, but they also have the Wild Shape feature that allows them to turn into a Beast during combat. The Wild Shape form has its own HP, AC, and attacks, so the Druid can be a reasonably effective melee combatant while transformed. This ends up as a "shifting role" character compared to the Sorcerer/Fighter and Eldritch Knight which each aren't very effective at the other's role.
If one of the other players owns the Xanathar's Guide to Everything supplement, the Hexblade Warlock might be even better. Warlocks have some significant differences from other spell casters, but a Hexblade Warlock with Pact of the Blade can be built as a very capable melee-range character with potent spellcasting, as opposed to Eldritch Knight having limited spellcasting options or Sorcerer being weak in melee. Non-Hexblade Warlocks can still take Pact of the Blade, but it would be much weaker.