most buyers who buy a car from Florida because they think it has had a salt-free existence aren't using their heads and think "hey, its a southern car, therefore no rust." Florida is completely surrounded by salt water and that salt does get into the air (ever sleep on the beach and wake up with that 'not-so-fresh' feeling? that's salt air for ya).

The best places to buy from, if salt-free history is what you are looking for, are those that are warm AND dry. i.e., no salt on the roads OR in the air.