It depends on what airport and port as well. In FFL a 11:30 flight is no problem. At Mia you are cutting it slightly close especially if there is a problem. In Port Canaveral flying out of Orlando, don't book before 1PM. Understand that until Homeland Security has cleared the ship nobody is getting off and they could care less about what time your flight is. They first have to clear the entire ship. That could happen by 7am if the ship docks at 4am but still unusual. Normally they start allowing people off around 8:30 or 9AM but I have seen it go until 11am a couple of times.