From what I've seen here, and my limited experience, if you buy liquor in port you will not have any problem taking it on the boat. However, they may take it from you and store it until debarkation. Some people have been able to take it to their room, but I believe the policy is for them to store it for you.
On board the ship they do have several different flavers of Barcardi. That is my favorite. It is probably two liters for about what you would pay for one in the U.S. If you are going to Jamacia they have a creme rum that is absolutely fantastic. They did keep it for us until the night before we disembarked. That was ok it was for gifts. On board all their liquor is less. You need to look at the size of the bottle.
Be sure it is packed correctly when you bring it home. We packed some in a newly botten suitcase just for the booze. Everything broke. Have no idea. The way we packed it I just can't imagine!!!!!!!!!! Anyway - carry it all on the plaine back with you. The airline crew will understand......
Probably any 151 would be a catastrophy then????? If you can't bring it back I suggest you sample as much as you can while you are there. It is fantastic!!!!!!!!!!!!!!! All rums in Puerto Rico are soooo good.
Usually CCL will NOT let you bring alcohol to your room. If not you can go to the pursers and ask for it to be delivered to your room. There are times you may get lucky but most times no. What I do is when I go ashore we buy our alcohol that we know will be taken from us but then also buy the little bottles. We then wear cargo shorts and put the little bottles in the pockets so we at least have some to drink while on the ship.