Sorry, but I don't know anything about getting a job with the cruiselines. I live in the desert so there are no ship positions posted around here. Check their websites or give them a call directly and they'll tell you what you need to do. Maybe post a new topic and title it something about shipboard jobs, and folks will be able to help. There are some really knowledgable people that read these boards.
What little I know comes from friends who work for cruise lines. The cruise lines decide what ship and itinerary you work on. And they can, and do, move people around, for whatever reasons they have. You really won't have any control over where you go.
But, still, check with the companies or other employees. You never know.