I have to agree with Lew, anytime around noon should be good, although I understand the pier and the airport in Ft. Lauderdale are right next to each other, so the ride to the airport will definately be a short one. Have a great cruise.
That time isn't engraved in stone. When we disembark depends on a number of things. We returned to Ft. Lauderdale from our Amsterdam Panama Canal cruise. It took one non US resident forever to haul himself out of bed and go to customs. He held everybody up. My daughter was on a 3:00PM flight to Washington, DC so she was fine. I live in Miami and just grabbed a cab. It didn't matter for us but anyone scheduled to fly before noon would have had problems.