Yeah, I don't see how the Sierra Madre doesn't feel post apocalypse. A location sealed up since the war, populated only by insane mad-max cannibals in gas masks and mindless machines still going about their preprogrammed routines? Secluded and hazardous enough so that it isn't looted? It's kinda hard to get more Fallout-y than that.

Unless your introduction to the series was Bethesda's Post-Apocalypse Theme Park, I suppose.