Our
DCL cruise that cruised out of Galveston encompassed all the worst things for us that has ever happened on a cruise. First, the air from PHL to IAH was outrageous, and I'm usually good at finding low fares. I guess Hobby was worse if we chose IAH. The port terminal had a warehouse feel, it's nothing like PC. I could get over those two factors if they're not important /relevant to you. But what put a sour note on beginning and end of that 8-nt cruise for us was the terrible motion sickness we got from crossing the Gulf to the Atlantic to the Caribbean, it was so bad in the aft restaurants that night, and I spent my life on small-sized sailboats and motor boats, never have I been so affected, even sleeping overnight on small sailboats . I laugh now looking back at our portraits from formal night, I actually look green.

But what was the worst part for us was how the cruise ended, the port was fogged in, we were stuck for hours in international waters without cell service, it was very creepy being able to hear the horns of all the nearby oil tankers but not be able to see them, with no clue how long we would be stuck there. We ended up missing our flights, but
travel insurance saved us when we had to book new ones leaving the next day and for our hotel that night. But not knowing what was going on or how long we were going to be stuck at sea was a little nerve wracking. Of course it was winter, and the only flights we could get connected through Chicago and of course there was an ice storm and more delays with that. A very, very exhausting 10 days. Anyhow, we love the Magic, and we love the longer cruises, so my only advice would be to see if you didn't have to cruise when the seas were too rough or port having a good chance of being fogged in, which I think is mostly a winter thing. There are plenty of people who cruise out of Galveston on other cruise lines besides DCL, and I doubt all their experiences were like ours. But maybe consider your travel dates and those few issues. Good luck!
ETA: we did not rent a car, we stayed at the Country Inn & Suites and had a shuttle to the port. We researched a lot regarding renting a car versus a private shuttle from the airport to that hotel. That was costly as well, but not as much as renting a car. Our driver stopped at a shopping center so we could jump out and buy a few things which was nice.