Hi Matlily. Welcome. It totally depends on what you want to do in these ports. Tours, diving, horseback?
My only advice..... Montego Bay, stay with an organized group. Do not venture off on your own in Jamaica.
I have been to all three places on longer visits but the folks I am travelling with have not. I think snorkelling is a must for cayman, but Jamaica I am not sure when Iwent last time we did the dunns falls but its so far from the ship port, so I think just beach stuff, have been told doctors cave?