We plan on getting a scooter for this trip. The Bakery has them so I guess see Dawn. Rebecca's Treasure Tours shows them on their web page too.
We had great service from http://www.treasurebeachonestop.com/ with the added bonus that your driver could be Kirk, Winston, or Mackie, the best bartenders at Alfred's in Negril during the 80's and 90's. Go to http://treasurebeach.net/guide/ and see transportation links and then motor scooter rentals.