I'm thinking about renting a car in Florence to drive through Tuscany and drop off in Orvieto. How many days is recommended? Any good off the beaten path towns to see? Any other advice?
From Florence, take the S222 south through Chianti. There are plenty of small towns and wineries to sample. If you base yourself near Siena you can make a circuit of the famous (and not so well known) hill towns. How much time depends on your interest, the time of year and your wallet.
I may also pick up the car in Pisa when I leave the Cinque Terra. This would be after visiting Florence.
We did this exact same route last summer. We picked the car up in Florence and stayed a night in Siena, a night in Montepulciano and finally a night in Orvieto where we dropped the car off. We then took the train to Rome.
When you leave the Cinque Terre, you could pick up your rental car in LaSpezia then drive to Pisa. Plan on a couple hours at Pisa. There is a church and museum as well as the tower to see. All buildings require tickets. The sight has a line of trashy vendor stalls around the area but they are NOT next to the area where you will walk to the sights. The hilltowns take awhile to reach even from the autostrada so plan the towns you want to visit carefully and look at the road maps. Very misleading. We spent 5 days driving and did not even begin to visit the towns we had listed. A full week would be good to spend in the Tuscany area and limit your area of hilltowns. We also traveled in November and lost an hour of daylight because of daylight savings time. November 1 is All Saints Day and some towns were "very quiet". Lots of families touring the hilltowns on this day.