For a flight at 11:30 you need to be at MIA NLT than 10:00 - and 9:30 is better with the typical TSA chaos. The ride from POM to MIA takes about 20-30 minutes, so that translates into off the ship, with bags, and clear of customs/immigration and looking for a cab or Uber/Lyft by about 9:00 - should be easy!