Yes, you will have time to make an 11:30 flight, but I wouldn't do anything earlier than that. If you have late dinner (thus, late breakfast), plan on eating on deck 9 and getting off the ship as soon as possible after the big doors open. It takes 45 minutes to drive to the airport, 10 minutes to go thru Customs, and the bus typically departs with 5-15 minutes of waiting to fill, especially early. The bus is definitely faster than renting a car (saves shuttle to car place, waiting in line for car, returning car, etc.)
Depending on your numbers, a towncar/limo service might be the same price or even cheaper than DCL transfers. It would only save you a few minutes, but you wouldn't have to wait while the bus fills up. Of course, if you are on a participating airline, DCL transfers will be fastest as you won't have to deal with the luggage at the airport.
We've been at the airport as early as 9am....but we've also been on a cruise where the big doors didn't open till after 9. Thus, NO flights before 11:30 under any circumstances.