I would not wait to much longer or you will miss out on getting a car. Tropic Car Rental I found to be the best, very clean cars and Hanes is a great guy very helpful like Andrea said you need to do it like right now. I did have some freinds that where able to rent a car at the hotel from Hertz but you will pay big time.
We Have booked with Royal a car for the month , I did email them and others re booking a car its the collusion waiver that costs so much, Gosh we do not have this in the Uk but must say we have found this waiver charge in other counties we have visited .As I said I did email serveral car rental companys ,we did get a better deal when booking to pay in dollars not by credit card ,every little helps . We did the Divi Time share once though the Tamarjin if you went you had a free car for 2 days but gosh we had to pay the waiver it would have been cheaper to have hired a car direct with a rental company!
We booked Hans over 2 months ago for a September vacation. I understand it is kind of quite in September, but we wanted a company we could trust (reading all the boards) and make sure we had a decent car waiting for us. Book NOW.