Key West is lovely in December. Fly in to Ft. Lauderdale and drive...it's a 4 - 6 hour drive depending on how many tiki bars you stop at along the way ;-). Lots to do there, although avoid the diving if that's something you do...not good there. Some good snorkeling spots and lots of sunset booze & music cruises, etc. Great restaurants, tons of fun bars, lot of history, eco tours, jet skis, and other non-drinking activities as well.