Personally, Siesta Key is one of my favorite beaches. It's about 2 to 2.5 hours away from Orlando but definitely worth the drive. The last time I went with a friend, the water was warm and we were in the water with dolphins a hundred feet away. If you want something a little closer (a little less than 2 hours), Pass-A-Grille beach in St. Pete is great too. Downtown St. Pete is pretty fun during the night with some good restaurants and stuff.