We did "Negril for a day" for years before we ever stayed in Negril. It's not even an hour and a half each way, so why not? I'd also do my own thing transport-wise. However, if you go with the cruise people they guarantee getting you back to the boat on time, if that's important.

I'm think you can take their ride to M-ville then meet up with them at Rick's when it's time to go. $70 pp isn't all that bad for round trip. You'll save money and do what you want with your own taxi, of course.

There are a lot of cool things to do near MoBay - Duncans, for instance, has a lovely near-deserted white sand beach to enjoy, with a little rum bar/restaurant by the fishermen. No cruise people there, I'm sure.

But I also know that if you have the jones to go to Negril, you might as well because you'll wish you did all day