No do not rent a car.
Unfortunately on Miami Beach its tough finding anywhere to park and if you do it will cost you up to $15. The hotels generally charge about $15 a day for parking too. Luckily 90% of the events, dining, drinking and tomfoolery will be taking place at The Palms (I pity their housecleaning staff!) when we do go off site transportation is provided.
If you do want to go somewhere on your own we always take cabs, its actually cheaper that way and there are tons of them around.