The port opens at 10:30am, I believe. Boarding generally begins between 12:15-12:30pm, which is earlier than the scheduled 1:00pm time.
It takes just over an hour to get to the port from the WDW resort. I'd try to get to the port at around 11:00am. That way you can check in and get a good spot in line to be among the first to board when they begin boarding. You can factor in having to drop off a rental car, etc. into your departure time.