Depending on how long you've got there, I recommend hiring a car and driving down to the keys for a few days/nights. Also try and check out a game of Jai alai 'the fastest game on earth' when you're there. If you're interested in american football, then go and see the Dolphins (although they're having a terrible season so far, currently 0-6). South Beach itself is very plastic and artificial but has some lovely art-deco buildings and a certain amount of charm, some great little bars, coffeeshops and some decent restaurants. When are you going?