I used AVIS. It was a short walk down the street from the ship (maybe 2 blocks?) no need for a taxi to get to the car. The rental agency is also a fishing/tackle shop
I left the wife and kids with getting the luggage checked in with the airlines and walked do to get the car and came back and picked them up. It worked well. Then returned the call at the airport.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007