preliminary Italy plans....

It seems you are planning on staying only one place, which is a GREAT idea for a stay of only 5 days. February weather will be unpredictable, as anywhere in the northern hemisphere.

Tuscania seems awfully small. I do not see any train service, so a car is a necessity. You'll be fine driving in rural areas, even without much knowledge of Italian language. I have to ask though, why Tuscania? Are you focusing on Etruscan sites? Viterbo is at least a little bigger with train service and more bus options. Or maybe Siena would be better: if the weather is poor you will find things to do in the city or can easily make your way to Firenze. From Siena you can visit many hill towns, although a bit further north. We like Montalcino, Montepulciano, Volterra, Greve in Chianti. Here a car is nice, too.

If you really want to stay in Tuscania, it would seem you should fly in and out of Rome. If you choose Siena or Firenze, then fly into Firenze.

The good news is in the off season, you should be able to find lodgign to fit your budget almost anywhere you choose.

Thanks Laurel,
Your advice is perfect! I only chose Tuscania based on its central location to some of the other towns we were thinking of visiting. But we could certainly stay somewhere else since most of these towns are in close proximity to each other. We were looking at this general region due to the high density of smaller archeological attractions, Roman baths, hill towns, etc. However, I'm going to spend some time looking into your suggestions as I have not yet come across these recommendations.

I feel a little better about driving there after your comments.....Thanks!

By the way - How is the traffic in Siena?

Sienna is one giant ZTL. If you are planning on driving, get to know these. Historic districts in larger towns have these to keep congestion down, (and collect hefty fines from clueless tourists).

My first driving experience in Italy was in and around Siena. Our B&B had a parking spot a 10 minute walk away, where we easily avoided the ZTL. We do say, though, that it takes two people to drive: one must mind the car and the other the signs.

This is invaluable information. I will do my research on ZTL's (and avoid them). Or maybe stay a short distance outside the city.

Are car rental facilities fairly common? Or are they largely located at airports?

Rental in Siena is by the RR station. I got a lot of good info and comfort about driving in Italy the first time from this report. The company, Gemut.com turned out to be a great resource and we've rented cars from them multiple times. For me, they beat EuropeCar and Hertz prices, yet I ended up with a Hertz car on a EuropeCar contract.
We rented in Siena and returned in Orvieto, FWIW. Both easy, convenient locations.

We also found Road Signs in Italy useful. Print it out and take it with you.

we just got back from our 4th trip to Italy and among other places stayed in Sienna in a small hotel near the Porta Roma on the southern part of the city. we had no trouble finding free street parking just outside the gate and we were only a 5 minute walk from the main piazza there in Sienna. We stayed in Sienna for three nights and took day trips to multiple hill towns. In towns like Sienna and Lucca you are allowed to drive to your hotel / B&B even if they are in a ZTL area to drop your luggage and then go park your car in a pay or free parking area. Your B&B will give you exact details. we did get stopped by a policeman in Sienna and he was fine when we mentioned the name of our B&B and that we were on our way back out of the controlled zone. Each of the walled or controlled area hill towns that we visited had multiple parking lots at the edge of the towns. rates were not at all unreasonable for parking. One caution about driving. There are a lot of small arrow type signs at the roundabouts and intersections when you get off of the superstradas or autostradas to actually get to your hotel etc at a town like Siena or any "hill town". You only have a second or two at most to find the sign that you are looking for and make your turn. rick is right on when it comes to roundabouts in taking several spins in the circle if you are unsure as to which road to exit the roundabout. In siena we had to deal with intersections not roundabouts. We had to know that the way to our B&B was off the street that had directions to Assisi vs the sign that pointe down a street signed towards Firenze (Florence. when in doubt pull in at some small gas station or similar and even if you speak no Italian and their English is limited they will find a way to direct you to the right turn

Would a car rental be absolutely necessary for this type of trip? An automobile in Central Italy is preferred, as trains often don't go to the hill towns.
I've seen the driving in Rome, will I die in a horrific accident if I try driving to the places I've listed above? Fly into Rome and take the train 70 minutes north to Orvieto. Hertz is across from the train station.
If we fly from Nice, would it be easiest to land in Rome and rent a car from there? To save expensive drop off fees, leave the car in NW Italy. Then take a train into Nice.
If there is a way to see these places without a car? Not really.
Would others recommend these towns or other areas? I prefer cities north of Orvieto, and staying in a central location (agriturismo) outside of Siena or San Gimignano. Day trips can be leisurely made to Siena, San Gimignano, Volterra and many other hill towns. You could also go into Florence (1 hr. drive.)
We do not speak/read Italian, will that be a challenge for driving (i.e. reading and obeying signs)? Roads are very well paved, if a little crooked. Road signs are well marked, and it's not hard finding your way. You won't find that many people speaking English outside of the tourist sites, but that's not a problem. Virtually every farm in Tuscany has rooms/apartments for rent as a source of secondary income. I'm talking hundreds and hundreds of great places to stay. I usually use Booking.com, as they have rooms about everywhere in the world.

Thanks again everyone! I'm learning a lot and processing all of this information. It's certainly going to make this trip more enjoyable.