Your flight will actually be AA1818. The outgoing flight is 1819. AA shows it to be a 757 with the same configuration for both legs so you'll most likely have the same airplane. FlightStats shows a 97% ontime record for the POS-MIA flight. You will deplane and claim your luggage pass through immigration and customs and recheck your bags. Even if you miss the flight don't worry because AA has constant flights to MCO and will simply put you on the next one.

This is an easy flight. Don't Worry, Be Happy. That's why you go there anyway, isn't it?