Good info from Sunshine3601. Each terminal will have a pickup/drop off area. Terminal C will be the busiest as it is United’s main terminal. I have seen the desk located in Terminal C baggage claim where you check in for the bus.
Have not yet booked; however, will need to for our Radiance cruise towards the end of April. DH calls Royal , gives our booking number and says he wants to add transportation from IAH to Galveston. Should be about $40.00 pp one way.
We recently had to use the service from the port back to the airport (had to fly to catch the cruise) as our car was there. We requested to be dropped at Terminal C As the bus approached the airport the driver announced which terminal would be first, etc.