We cruised the caribbean on the sea princess last january. we didnt book any of the trips via the ship, but did them independently. we either asked another couple to join a taxi with us prior to disembarking or if we saw anyone standing about waiting for a taxi we asked if they minded us sharing with them. we went round most of the islands this way at a fracture of the pric.
I too am travelling on the same cruise as you and when I went to book online the other evening for a couple of trips I wanted to go on they were fully booked. I am travelling alone and have been told that all islands are accesible on your own via taxis. I dont wish to intrude but Prehaps we could meet up on board and see if we could share taxis etc etc. Jenni.
Most of the caribbean ports of call are very accessible and on some you wont need a taxi 9water or land based) you can just walk in to the main town centre.