Disney recommends that you not book a flight before 12:30; I wouldn't book before 11.
Yes, is all goes well, you can leave the ship at 7:30 BUT that assumes normal Customs clearance. I've been on 3 sailings when we didn't clear till after 8:30; on one of those it was about 9:10. The problem would come in if you planned on 7:30 and the ship didn't clear on time....you need to allow at least 30 minutes to pick up the rental car, 45 minutes to drive to MCO, and 15 minutes to turn in the car. MCO is one of those airports where they recommend that you arrive 2 hours before your flight. While I've had times when it took 30 minutes to check luggage and go thru security, I've also had flights where it took every bit of that 2 hours!
Back to the ship...if all goes will, it takes you 2 minutes to walk off the ship, 10 minutes to claim your luggage and go thru Customs, and 5 minutes to wait for the shuttle to your car rental. Of course if you want to get off at 7:30, you'll be in the first wave of guests and you could stand in line for 10 minutes before you get off the ship and another 10-15 waiting for a Customs agent. Bottom line, from the minute you leave the ship till you are in your rental car COULD be 20 minutes, but it could also be an hour. Don't cut yourself short!
