Car rental in Florence

Try airport or railway station. If renting at the rail station, get a map showing the way out of town to avoid any TLZ.

I am staying at Salvadonica for three nights at the beginning of May. When you pick up your car, make sure the provide the exact routes for both leaving Florence as well as when you are returning the rental. The will provide the routes that avoid the ZTL.

Also, the staff at Salvadonica will also provide you with information regarding where you should park in the event you are heading into Florence for a day to also avoid wandering into a ZTL.

You should be fine to pickup your rental car from a Florence city center location. Most small cities don't have car rental locations.
We caught a 2 mile taxi ride from the Florence train station to Hertz's location at 53 Via del Sansovino. Our reservation was made through AutoEurope.com for slightly less than Hertz.com.

They gave me directions to get through Florence and Hwy A1 south without getting near any ZTL's.

I didn't find traffic inside or outside the city to be difficult at all. You're not going very far, and it's a straight shot down there on a 4 lane highway. The roads of Chianti and Tuscany are well paved, and they have good road signs pointing you to your destinations. We navigated throughout the region even without road maps.

We turned our car in at Orvieto, north of Rome, and caught a train into Rome Termini.

Are you staying in Florence before picking up your car? Are you flying into FLR that day? or arriving at the station? Do you have a lot of luggage?
These are the options:
1. Rent from the airport. This option is viable only if you are flying in and renting a car upon landing. However consider that picking up a rental car at the airport will result on a higher DAILY rental rate, therefore it is often cheaper to take a taxi into town and picking up from there, if the taxi fare is less than the additional cost you would incur from renting at the airport. The taxi fare to town is no more than €25 euro.
2. If you are staying in town prior to renting and you plan to walk to the rental car office, the Hertz office in the city center is located on a street called Borgo Ognissanti, about 10 min. walk from the central station. Driving out of there is very easy and there is no chance of being photographed by a ZTL camera. You have just to drive west on via Borgo Ognissanti (the street is one way going west). The street changes name and becomes via Il Prato after 100 mts. Continue 500 mts on via il Prato. Turn right (only direction allowed) at the Il Prato City Wall Gate onto viale Fratelli Rosselli. Turn around (like a U turn) on the same blvd and head southwest all the way to the freeway.
3. The easiest option, if you have luggage and plan to go to the rental office by taxi, might be to go to the Hertz location on Via del Sansovino 53. From there drive SW to the freeway entrance (left when exiting the rental lot). At the A1 entrance (called Firenze-Scandicci) follow the directions to Roma. You will be exiting at the very next exit (Firenze Impruneta). Pay toll and follow directions to Siena. You will now get on another 4 lane freeway.
Exit at San Casciano exit.

Great help, thanks so much. We will be staying in Florence for 3 days before renting car. I plan on picking up at Via Maso Finiguerra 33 Hertz office. This doesn't look too far from the train station, then driving to Salvadonica. I may look at dropping off in Orvieto though, that sounds like a great driving experience.

From via Finiguerra turn right on Borgo Ognissanti and follow the previous directions. As you cross the river follow the green signs to A1 Autostrada.

Salvadonica is in Mercatale. You will be just 10 min. walk from where the "Monster of Florence" (serial killer) and his accomplices lived. Lock the doors at night :-)