We are scheduled to arrive at the Galveston port on November 16. I received a rate of $47.15 out the door from Enterprise from the Galveston port to Hobby airport, with no drop off charges.
I chose this option because it will give us an opportunity to see some of Galveston and maybe the Johnson Space Center. Our flight leaves Hobby at 3:25 PM and if there are any flight delays we won't be waiting around the airport.
From some people we met who live in Houston, it is about 45 minutes from the Galveston pier to the Hobby airport.
Hope that this helps,