If it's crap ... We'll tell you
I almost want to say New York, but that's too generic.
Maybe Florida? Seeing chard palm trees could be relaxing. Or Hawaii.
I really don't know what else they could do out west so I'm guessing they focus on the east coast or maybe the middle of the country. There were a few storylines in Fallout 3 for the Institute in the Commonwealth that were implying that the commonwealth may be the most technologically advanced region in post apocalyptic America so I wouldn't be surprised for a New England area setting. Other than that, New York and Chicago are probably still on the table and maybe St. Louis or Dallas if they decide to stick with the middle of the country. Assuming they don't hop over to Europe or something.
Chicago would be cool. I'd just like to see a much less procedure-generated landscape this time, but that's probably a lot more effort than Bethesda would put in.
Japan, just so we can see how screwed up it is after the apocalypse.
They could make some amazing tentacle monster scenarios.
And start making us loot from broken panty dispensing machines.
Panties could be currency instead of bottle caps.
I'd like to see maybe China or England.
And while I live in Texas and may be able to identify more... eh... All our major cities are already desolate waste lands of gangs and death.
Except Austin... but unlike the Spill crew, all none Austinites would love to see it removed from the face of the earth. Pretentious hippies/hipsters...
I'd like to see them set the game in China. They were the force fighting the US which caused the nuclear apocalypse, and it would be interesting to see how their society has fared. I've always had this idea playing around my head that maybe some of the other countries are not complete wastelands, and just steer clear from America because of how irradiated and lawless it is. Maybe the plot would involve them foraging for potential resources in the States?
In Orlando. You can't get a more screwed time to go to disneyland.