We drove to Galveston since we live near San Antonio. I parked in the EZCruise lot. The price was $35.00 for a four day cruise. They take you and your luggage right to the terminal and drop u off at the baggage check in gate. There are other cruise parking lots; Lighthouse, Poet of Galveston and a few others.
Passports don't matter much getting on the boat, as everyone goes through the same line. But for debarkation, passport holders go through a much shorter line. It didn't make much difference to us since we drove to the port, but if you had to catch a flight, having a passport or passport card would be a definite advantage