Obviously the skyscraper scenario does kind of work. While not a skyscraper, the Atlanta PD had a decent setup at Grady Hospital (if you 86 the rape and other acts of douchebaggery) and there was the nursing home situated in Atlanta. So, we can assume if there are two buildings populated by living humans, then there are most likely more scattered about. Same with New York City.
You would think a podunk redneck town in, say, Montana or Kentucky would be an ideal place to be during any sort of apocalypse, but looking at the evidence on the show, Rick's little town didn't survive and Woodbury (besides a couple of streets) fell too. People here in the boonies freak the fuck out for no reason (case in point the recent snow here). People go full on redneck in about 5 seconds and have no common sense to boot.