The port opens to incoming traffic at 10. If you arrive before the port opens, you will have to park off the property till it opens, so if you are in a taxi or limo, you do not want to do this. The counters open for check in at 10:30. Boarding is scheduled to start at 11:45.
We usually arrive just about 10:30 or a few minutes later. This puts us near the front of the line to board, although not right at the front, and gives us plenty of time for ressies, etc. when on board.