That's probably the worst location ever, a city could work, but only if it's a small part of the map. The people will need food, and as such they need farms. Also, there has to be a high degree of civilization. The thing with humans is that, people don't like to sit all alone in their mudholes. People will cluster together, forming small groups capable of taking care of the entire group, with farmers providing food, and security forces guarding the settlements. That's how humanity works, and that's the way it has worked in all previous fallout games (except FO3, but that's the odd one). FO3 had an excuse by being located in DC, a former capital, complete with lazy good for nothing politicians.
in FO3 the city and outlying areas took up 1/4 of the map, which worked ok considering the other cool locations, the entire downtown area was pretty cool, seward square, la enfant plaza, takoma industrial, the capitol building, so they'll duplicate the basic idea i think, i can't see them making a less detailed city than in FO3, actually that city could of been better i think, but they wanted it all superdestroyed i guess, people like exploring abandoned/deteriorated cties, actually todd howard said in an interview, the downtown area in FO3 was gonna be even bigger, but they had to keep making it smaller and smaller because some of the designers thought it would be too complicated. so it was smaller than it was originally gonna be.