Hi Chris:
A couple alternatives to regular route taxi's to get around the island:

Knutford Express bus - air conditioned service between MoBay and Kingston (via the north coast). Very reasonable and with a fixed schedule. For rates and schedules visit their website at www.knutfordexpress.com.

Southcoast Express - a/c service between Negril and Kingston (thru Mandeville & Sav). Their website does not seem to be operating, but their telephone number is 876-966-2826. Again very reasonable and with a fixed schedule.

Enjoy your tour - I have been around the island on mini buses many years ago and thoroughly enjoyed the experiences.