I have arranged a rental car out of Florence, in town for my travels into Umbria. It will be returning it to FCO, Rome on a Sunday. I thought I had arranged a car at the airport, but apparently the reservation is in town. Avoiding restricted areas is crucial. How hard is it to find your way out of the city, vs. the airport. If I go to the airport, I would take a taxi or bus.
We picked up our AutoEurope car at Hertz on Sansovino. They gave us directions to get out of town without getting close to the ZTL's downtown. I caught a cab at the train station for the 2 mile ride to Hertz. I avoid airport rentals as they'll always pack on carrying charges and taxes you won't have in the city locations.
Driving thru Tuscany is no problem if you can handle a straight shift. The roads are well paved, if a little crooked. We followed road signs and didn't even have any road maps or GPS--and had no problems.
Many will turn in their car in Orvieto at Hertz and take a local train into Rome Termini--70 minute ride. I would suggest you take a bunch of pictures of the rental car as few locations are open on Sundays--but have a key drop off.
I looked at dropping the car at Orvieto, but the Hertz isn't open that early on Sunday, or late on Saturday for that matter. That led me to consider driving to FCO to drop the car. Thanks for the info.