Jerry and I are the ones who drove 1890 miles to the cruise, Northern California to Galveston. We had a great trip, stopping along the way at Schulenburg, TX, for some great BBQ and also at Sonora, TX. If Sonora is on your way, make a stop there, the downtown is not to be missed. Very well restored. If you are very lucky (and we were), the "downtown lady" will give you a personal tour.
We stayed several days in Galveston before the tour, going to Moody Gardens Rainforest Pyramid and the Railroad Museum. If you are a train buff, this is not to be missed.
We got to the port at 10:30 AM, and Jerry dropped me and parked in the Port Parking Lot. You pay in advance ($80 for 11 days, which is reasonable compared to California ports), and they run a continuous shuttle. You have to drop your luggage at the ship first, there is no luggage allowed on the shuttle.