Technically, you could choose the Infiltrator archetype if you didn't have Favored Enemy - its prerequisite is the Favored Terrain class feature. But, you wouldn't get any benefit from it (and would lose Favored Terrain).
At 3rd level, an infiltrator learns how to copy the unusual abilities of his prey. He chooses one type of creature he has selected as a favored enemy, such as “aberrations.” The Ranger selects one ability or feat from the adaptation list for that type (see below). A Ranger can use adaptations for 10 minutes per day per Ranger level he possesses. This duration does not need to be consecutive, but it must be used in 10-minute increments.
Step 1: Choose one type of creature you have selected as a favored enemy.
"So, I can choose any one of my zero favored enemies... why did I choose this archetype?"