Ocho Rios is usually one of the port stops on most seven day cruises. You will hear a lot of controversy about Ocho Rios, both pro and con. You should be able to do a search on the ports of call section and find plenty to read about Jamaica.
The most popular thing to do in Ocho Rios is to go to Dunn River Falls which can also include tubing as an extension of the excursion. You want to use common sense precautions in Jamaica just as you would in any port. Don't flash money or jewelry around, be aware of your surroundings, and say a polite firm "No", to street vendors and move on. I would stay with organized tours or go with a group. Don't wander off on your own. There is no reason you can't enjoy Jamaica.