Car Rental for Tuscany-Yes or No?

I suggest that you use the search box at top center to get the widest variety of opinions about your questions. That will help you decide, and also collect useful facts, like "ZTL" and "IDP".

I'm not wild about driving far away from home, but there are some locations where having a car is very helpful. Tuscany is one of those places. The car also doesn't have some of the downsides that you have in, say, England - you drive on the right in Italy, and most of the local roads are wide enough for two cars to pass each other. You still need good walking abilities, because much of the parking is on the perimeter of the hilltowns, and the towns can have steep sidewalks. OTOH, the car limits what you can do at wine tastings.

If you post again, be sure to give the month of the year, and describe the character of accommodation you imagine. The volume of luggage you have affects the decision about where and when to rent the car. Have you read some of Rick's general travel notes (like not leaving stuff in the car .. ) at the top left?

Thanks Tim. We will be traveling the first week of May, and we will have very low amounts of luggage (one carryon/person.) I have been concerned about ZTL, etc, which is what making me hesitate.

Tuscany is one of those places not really well serviced by trains, and so many hilltop cities are off the beaten path.
We usually check with AutoEurope.com and Hertz.com and rent from the cheaper of the two. AutoEurope cars are often picked up at Hertz or other famous rental companies.
The roads in Tuscany are very well paved and easy to navigate. They're just a little crooked when you get on the back roads--off the main routes. But American drivers won't have any problems driving the region.
We picked our car up at Hertz on Sansovino in Florence--2 miles by taxi from the train station. They gave us directions to the motorway going south, and we were at our agriturismo in maybe 45 minutes. Airport rental locations always come with extra surcharges and taxes, so we prefer to rent in the cities.
My only problem was with a radar/camera on the causeway going over to Venice. They caught me going 1.2 mph over the 35 mph speed limit--even though there wasn't another car in sight. The day was worth the ticket received almost a year later.
FYI: Siena is very congested, hectic and parking is hard to find. It's better to catch a bus across the street from the Florence train station and they'll take you into the center of the city.

You need a car for your Greve portion of the trip.
Can't go around that or it will be inconvenient.
You won't need or want a car while in Florence, therefore pick up the car at the end of your Florence stay.
ZTL (Zona Traffico Limitato) are well signaled everywhere. Do a Google Image search to see what the sign look like. It's generally within the historic core of a town, often surrounded by ancient city walls. Just park in the parking lots outside the perimeter.

Roberto is right on. I rented in town once and now I go to the airport. Easier but might be more expensive. Wait until you are ready to leave Florence, rent the car, and enjoy driving in Tuscany. It is fun and safe.

You have maximum freedom to see many, many site with the car.

Yes, you will car very handy for those 3 nights in Greve ; but not before. We rented from the Europcar office in downtown Florence, address is Via Borgognissanti, 53/55/r, 50123 Firenze, Italy

You really will not see the famous countryside views without one.

The booking was through Auto Europe and from that location the drive out of town post checkout was not difficult, just make sure to ask for directions out and follow them. You really would have to backtrack or turn around to run into a ZTL as they are monitoring cars entering not leaving if that makes sense.
We easily drove from their to Siena and Siena parking and avoiding ZTL was a breeze if using the Santa Caterina lot and taking the escalators up to the city ; which was fun and avoided a steep walk too.

Here is that address, it was easy on and off a highway exit.
Via Esterna di Frontebranda, 53100 Siena SI, Italy

In terms of ZTL concerns many thing to tell yourself and remind yourself over and over that in Tuscany outside of big cities like Florence is that the only ZTL's are inside ancient walls which are easily scene. Don't drive inside any wall openings and you really cannot stumble into a ZTL in the smaller hilltop towns in Tuscany including Siena.