My next cruise is the Carnival Conquest out of New Orleans November 6, 2005. Several of my cousins and I are going. Hopefully we'll see Montego Bay, Georgetown and Cozumel. On my last cruise, RCCL's Rhapsody, January 2, 2005, we ended up in Miami to refuel and didn't get to go to Grand Cayman.
Hobby is your closest airport. It is south of downtown Houston. 30-45 mins to port depending on traffic. Houston Intercontinental is north of downtown and probably a 1-1/2 hour trip to Galveston (which is south of Houston).