Aside from working on a cruise ship (which I do, and it's no vacation), many Vegas casino's give out cruises as top prizes (check out Terrible's on Paradise Rd. - they give out a Cruise every week)....
A cruise port or port of call is simply where a cruise ship stops. The Embarkation Port is where the cruise starts. The Disembarkation Port is where the cruise ends. Often those are the same. The...
You question is a bit vague. If you're asking about the Port of Embarkation, Miami is the biggest port in the U.S. for Caribbean Cruises. San Juan Puerto Rice is right up there as well.