We always take Carnival excursions and for the most part feel they are well worth the money paid. We don't have to hassel with finding someone else to book through, worry about when we get off the ship and whether we'll make it to our appointed destination on time or if we'll get back to the ship in time.
I'm not sure what ports you are considering Western Caribbean so I can't address those specifically.
I would like to know which ports you are going to....are you just doing the "regular" western or are you doing the Exotic western?
In Grand Cayman we took the excursion to Sting Ray City....we went on the first trip out that morning (there were two times) and got to see this wonderful "dark" underwater cloud as it moved towards us in the sea foam green water. Then being in the water with them up close and personal was remarkable. The sunlight playing pattern games on the sand underwater. The whole experience was spectacular. I so wished our sons had been with us on that cruise just for that excursion.
Grand Cayman....definitely the Sting Ray City...one of the best excursions i've ever been on....Standing in the water...and they swim right up to U...U get to feed them....very very gentle creatures.....
Ochios Rio.......any tour that includes Dunns Rivers Falls......Climbing the falls was Fantastic....also don't forget to check out Margarieivile (sp)...it's within walking distance of the ship