The port terminal opens at 10:30 am, I think. Boarding time is scheduled for 1:00pm, but the reality is that they usually begin before that. In my experience, it is usually between 12:15 and 12:30. It really depends on how quickly they can get the ship "turned around," that is, cleaned and ready for new passengers.
I usually eat a light breakfast on the morning of the cruise, but no lunch. They have a great lunch buffet (mmm...peel-and-eat shrimp!) which is open once you board.