Update…. I too will be on the Allure in November. The parking at the Port of Galveston is $168 (retail). I booked at EZ Cruise Parking for $90.00 and they will shuttle you to the port.
The port of Galveston is also building parking for the new terminal. It is called “North Parking” and you can reserve for November. I do believe the existing lots are too far.