The one at Royal Pacific (fitness center desk) opens at 6:00am........it's amazing to go down there sleepy-eyed to rent a cabana and see all those wide-awake people running on treadmills already!! At RPR, you can reserve one any day before you actually want one though....you just have to pay for it in full to hold the ressie. And there's no refund if it rains. Don't know how the other 2 hotels work.