The cab from the airport to the hotel is in the $25 range. The hotel to the port is probably $20 (there is a port entrance fee they charge the taxis which in turn pass that charge to you so it is a short distance but about the same costs. The time you go to the port is also a factor as the taxi line may be long if you go when everyone else is there and the clock is running. Then figure in a tip also...
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, Celebrity Silhouette 2013