What's all this florida crap? I'd rather see New Orleans or Texas if not California.
Maybe even Arizona or New Mexico.
If its done by Obsidian then yes to Arizona(Flagstaff in particular) because they can handle that lore heavy region.
I feel that if Bethesda makes Fallout 4 then they should do it in Florida. That might just force them to come up with their own ideas, instead of recycling from the originals.
I'd trust Obsidian with New Mexico, though Bethesda should stay as far away from it as possible partly because it's near the lore heavy west coast, but mostly because of an irresistible urge for them to include Area 51 which will inevitably lead to more insultingly stereotypical little green aliens.
Texas contains...bad memories of things best left unmentioned.
I have no personal opinion on New Orleans, though it could be interesting.
California should be avoided completely by both companies. Its been in two of the games already and it is the centre of the NCR's territory which would make any game set in it more then a little dull.