Hi,
just to quickly add that a lot of the car rental companies have changed their toll programme again recently.
The details are all here:
https://www.sunpass.com/rentalcarAt least Alamo have limited the convenience charge to $6 max now, and the charges are the same as what you would have paid in cash.
I think there had been some problems with trying to register hire cars with the sunpass boxes you can buy at the supermarkets, as the number plates were already registered, so they seem to have dropped that part now and just go with the toll-by-plate method.
We've used it last week to drive back from Florida City to Clermont - took us approx 4 hours 15 mins. We did drive all the way back from Key West a couple of years ago too, in about 6 hours. Great if you just want to get somewhere, but as others have said, there's so many other place to go and see on the way.
Hope this helps.
