Don't know if you've hired a car in the US before but we went there a few years ago - flew into Sanford and hired with Dollar.
Anyway, reason for the reply is watch out for the insurance & taxes which are extra and only appeared after our rental period, we nearly fainted at the credit card bill and had no come back.
There is an airport tax - as they are located at the airport
A tyre tax - recycling fund for tyres
and the list goes on and on...various types of insurance, theft, tyres, windscreen etc
Nicest salesman ever (while fleecing us) but we ended up paying an absolute fortune for our 'free' upgrade.
If you go fly-drive make sure it's a decent car with air-con before you go as upgrading might be quite expensive.
The fly-drive usually only covers the hire of the car not all the insurance & extras.
Hope I haven't put you off, it's an amazing holiday but just better to be prepared!