The Keys are great, I'm from SW FL originally, and I like that the Keys tends to be where the locals go to vacation, has a lot more laid back vibe. If you do wanna get turnt up then hit up Key West. It's like a mini-New Orleans
With one week you've got to keep traveling and jet lag in mind, an amazing week on the beach in Thailand can be messy once you consider 16 hours of travel time and some weird jet lag. I like looking North/South a bit, Canada/Mexico, a great way to travel for less time but still get that "away" feeling for the whole week.