It looks like most lines are strict about this, however, in port is another story. Remember, you are visiting a foreign country when you go to most ports, expecially in the Carribean. Each country has its own laws and regulations which you are subject to. The only thing the U. S. embassy can do for you is to make sure you are being treated humanely while in prison, and give you a list of local attorneys. Contact either the State department or the embassys of the countries you will be visiting for information on liquor laws.
It sounds like you are between 18 and 21 or possably younger. My advice would to be EXTREMELY careful with alcoholic drinks. The overwhelming majority of sexual assaults on college campuses involved alcohol. Remember, you don't have to be drunk to have a good time. I've been there, done that, AND I'M NEVER GOING BACK!