I'd say it's too early from what I've read on other boards. Some people have had to wait in line a total of three hours (1 1/2 to check in and 1 1/2 for security). There is a post on the Princess board on another unnamed board pertaining to this. San Juan apparently is notorious for lines.
I'm getting off the Adventure of the Sea on Sunday the 4th of April. I have a 12:37 flight back to states. Do you think thats too early? Sure hope not cause I couldn't find another affordable flight except for that one.
as the others have said, San Juan airport can be a mess. I would not book any flights before noontime.
Charisse - i think you will be ok, just inform the cruise line of your flight time and ask for an early disembarkation time, the cruise lines are usually pretty good about this kind of stuff. If in doubt, spend the extra$ and purchase a ships transfer to the airport.
We had a 9:30am flight out of San Juan in March 2003. Princess had ups meet early and had no problem getting to the airport. Cabs are right there when you get off the ship. They did want a copy of my flights to make sure I had early ones. There were about 30 other people in the same situation and they all got off in time as well. The nice thing was the airport was not busy when we got there and it was a breeze checking in.