Yes, Orlando is the fastest way. You can rent a car in Orlando and drop it off at Port Canaveral (they have shuttle service from the rental car companies to the port) for about the cost of one cruise provided transfer, so if there is more than one of you, you can save money that way.
West Palm beach would be the next closest airport but it is further than Orlando and there are more flights going into Orlando than WPB, but if you can get one cheaper into WPB, it is an option.
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