The Hilton Garden Inn has a free shuttle to Rome too. You have to be at the airport 3 hrs before your flight, check to make sure the shuttle runs that early to Terminal 5.
To the top right is Top Questions, have a look at Driving in Tuscany. You don't want to have a wonderful time in Tuscany and a year later start receiving tickets for entering the dreaded ZTL's or bus lanes. You should also get an Int'l Driving Permit from AAA, $20 and take a passport type photo. (you don't have to be a member) It basically translates the fact you do have a valid State driving license.
If your flight leaves at 09.00, you need to be standing in the check-in line by 06.00. Stay at the airport.
