Car not needed in Florence, definitely need it for outside Florence
Ciao Tindlin,
In my very personal opinion, May and September are both the best months of the entire year to be in Tuscany. In May, the flowers are in bloom and the countryside is green and in color while the the temps are not too hot or too cold - dress in layers in any case.
September is generally a bit warmer but the crowds from the high season are clearing so it is also a great time weather wise. We've also sometimes had spectacular Octobers with warm sunny days but definitely these two months are the best in general.
How long will you be able to stay in Florence/Tuscany? If overall you have enough days, you could divide your stay in two - first spend 3-4 days in Florence, then move out into the countryside. That way you don't need a cart while in Florence and rent a car just once you move out into the coutryside and use it to do day trips around Chianti, Mugello, the Val d'Orcia, Maremma, along the coast... all depends on how many days you'll have!
You'll find
small apartments both in Florence as well as in the countryside. In Florence, you can check out apartments directly from the owners or even small residences that offer apartments for your stay - check these three out as a start:
Apartment Pergola and
Palazzo La Medicea are very centrally located near the Duomo, while
Apartment Oltrarno is a little further away (still within the historical center though).
As for outside Florence, many villas and farmhouses offer either rooms (with B&B setup) or apartments where you'll have your own kitchen or at least kitchen nook. Take a look at these just to get an idea - all are
apartments in Tuscany rented from the owners! Here, the hard part will be deciding whether to choose a place you like and going there or first choosing a general area and then looking for apartments there. If you have a car, you can practically stay anywhere central to make day trips in all directions no longer than 1-2 hours drive.
Generally all the terms for the rental is set out from the start so that you don't have to worry about hidden fees - if some charge extra for something, such as A/C, they'll generally say you pay for the use you make of it and tell you how much you'll be charged. As far as A/C goes, electricity is really expensive in Italy and A/C is not that commonly used even if it is becoming more common lately. So just be aware that if you pay for use, use it with moderation so that you won't have an extra bill at the end of your stay. In May, A/C is not generally needed at all, just using it as an example of something that generally could be extra ;-).
Feel free to post any other questions if I forgot something or you need more suggestions in narrowing down your searches
