A few more thoughts....
As stated above, the bus is a full size, restroom equipped intercity bus. The times I have ridden it the driver played (forgettable...Paul Blart Mall Cop?) DVD movies. (OK, so National Treasure 2 wasn't so bad....) The stop in Nacogdoches is made at a truck stop and is generally about 20 minutes long; long enough to visit a real restroom and pick up some refreshments for the remainder of the trip. The stop in Houston is made at the Amtrak station; while there isn't much in its vicinity there are restrooms and vending machines if you just must have something more to snack on. (Make sure that the driver knows you'll be in the station....)
The museum/bus stop in Galveston is located at the head of The Strand, a very popular historic district with a number of bars, shops, cafes, and restaurants. It's safe and walkable day and night. My own "must-see" on The Strand, aside from the Museum, is
La Kings Confectionary two blocks up the street...an old-fashioned ice cream parlor and candy factory which makes the best banana splits and ice cream sodas in town.
If you decide you would like to spend a night in Galveston before or after, the
Tremont House is just two blocks from the Museum. It's an upscale Wyndham property; a bit pricy but very nice inside. Their rooftop bar overlooking the harbor is "not to be missed" if you're in town at sunset.
For lunch I always recommend
Star Drug Store a few blocks south of The Strand on 23rd St. While no longer a working pharmacy, it does have its original old-fashioned lunch counter serving sandwiches, burgers, and ice cream treats which rival La Kings.
If you make a day of The Strand, be sure and stop in to see Galveston's "tall ship", the 1877 sailing ship
Elissa.
