The trip usually takes about an hour, probably a bit less. It is about 50 miles from the port to the airport. Bear in mind that once you leave the ship, you have to find your luggage and go past the Customs officer. This usually takes 15 minutes or so.
How early you have to leave depends on your flight time. We typically get off the ship between 7:30 and 8:00, after it has cleared Customs, and are at the aiport and through security usually between 9:45 and 10:15.