Personally, I would just simplify things and get the car at the airport and drive out to Tuscany from there. It is a relatively easy route from the airport - all highway/autostrada (with tolls, so make sure to have some euros before you leave the airport) until you get to your exit for Tuscany.
When leaving the airport just continue to follow the signs for A1 Autostrada Firenze. You will be making a few exits until you actually get onto the A1 but just continue following the signs in that direction. You will first go on the GRA highway (the big ring around Rome) and then eventually hit the toll booth where you will take a ticket.
We just spent a couple days in Rome before a week in Tuscany and on. We left fom Ferrovia. Signage in Italy is pretty bad and driving there can be a little bit of a challange if you have never done it before. One thing to remember is when you are approaching a toll booth to pay your toll make sure you get in the right lane. Some lanes have machines to take bills or credit cards, some have toll collectors (quickest and easiest) and some require a pass to open the gate. You can always pull over to the right and survey the situation before you get to the stop. When passing get over when you can as even in the countryside people will tailgate you untill you get over. There is always construction in places so you will get some advance notice to get over, but not as much as you are used to. None of this is a big deal, just some observations.
Depending when you leave the Rome airport heading for Tuscany. you may want to take some back roads through Southern Tuscany, depending where you are staying. You can take freeways/autoatradas all the way to Siena. Arrezzo, Pisa, etc. Or you can take the Autostrada to Chiusi and get off and enter into Tuscany through the Montepulciano, Pienza areas and north to Siena on the R2 (if indeed Siena is your destination.) Much more interesting than driving the freeways, but slower! Hope this raises some alternatives.Edited: 04 November 2011, 22:58
Car, no question, and with this itinerary you have the perfect chance to see a lot of the region assuming you pick-up at the airport and drop at Civitavecchia for on your return you could drive south down the coast road. May I just pick up on a couple of points Glaciermeadows makes. Re signposting, it may not be as great as in the US but by European standards Italian signposting is remarkably good, I'd say it's certainly more comprehensive than in Britain, especially in the country. The point about the autostrada toll gates is a good one and their observations that it's invariably quickest to get in the queue that's indicated by a signboard bearing a hand (ie it's manned) is spot on. Something however that drivers need to pay close attention to - when you leave the toll gate having paid your toll, look out for vehicles exiting through the Telepass line for they'll be driving quite fast not having had to stop and a good majority will be large trucks. Be especially vigilant at Val di Chiana (the exit on the A1 for Siena, the Val d'Orcia, Perugia, Cortona even) because if you're heading to Siena, Perugia, Cortona you'll need to be turning right and cutting across this line of fast moving traffic. You will find roadworks on the highways in places but warning signs are given well in advance and even, I think, in English (men at work). Let's be grateful though for at least it shows there's still money to mend the roads. When we no longer see them fixing the carriageways, then we'll start to worry.
I question whether it is wise to get off a long-haul flight, rent a car, and set off on a three-hour journey involving a substantial distance on a motorway carrying fast and heavy traffic.
My thanks to all!! ...will give all advice much thought.
I would give considerable weight to the location of your first overnight stop: if it's a very small place which requires access by car, or a larger town. For example, if the first overnight stop were Montalcino or Pienza, renting a car at FCO might make more sense than if you're overnighting in Orvieto or Siena (linked to Rome by excellent public transportation). Similarly, if your first overnight were in Pisa or Lucca, I would be more inclined to travel there by train, especially since the drive is long, most people are quite jet lagged after a long transatlantic flight (possibly with delayed reaction time), and for some people, the route by car may also be a first time experience. Unfamiliarity with driving conditions and customs, renting (perhaps) a manual shift car, and lack of sleep after a long flight, are sometimes not the optimal harbingers of a safe trip.
We just got back from a month in northern Italy and the Dalmatian coast. We put 5000 km on our leased car.
I would not recommend that you pick up the car after landing at the airport from an overnight flight. You will probably not be in good shape to drive and driving in Europe does have some differences from here. For sure, learn the international traffic symbols before going.
Because the prices were best for flying and for our car, this last trip we landed in Nice, stayed in an airport hotel overnight and picked up the car the next morning. This worked very well.
Rome is a bit more complicated because there are no inexpensive hotels near FCO to my knowledge. You have a few alternatives: (1) Fly to Rome, take the train into the city for a night and then either back to the airport for the car, or (2) rent the car in Rome. I have read that some of the car rental places in Rome are located within easy access of the autostrada. With a good map or GPS this would work. Or (3) take the train to Florence or Sienna, visit it and then rent a car for the rest of Tuscany.
Will you be able to drop off the car at Civitavecchia or are you planning to spend time in Rome before your cruise? If you want to see Rome, it would make sense to visit it first and then drop off the car in Civitavecchia. Or you could finish in Rome and take the train to the port, avoiding the very high transfer costs. I have taken the train and if you can handle your bags, it is a great way to go.
One week is very little time for Rome, Florence, Sienna and the rest of Tuscany so you have some hard decisions to make.
I have been to Italy several times now and still have much more to see and do in this wonderful area.
You have gotten some great advise. It is great that Italy is doing so much repair work on their roads! They do give you fair warning. I found that when you do get to where you have to merge it is a quick merge and not gradual, so you have to be prepared. Cars in italy are comming faster in the left lane, so when you suddenly have to merge it can be a little difficult. This trip we were in Amsterdam before we got to Rome after a long flight from Seattle. I do agree if you are not used to driving in Italy driving after a long flight can be a little disconcerting. We were going to take the train from Rome to Chiusi and rent the car there for our drive to Montepulciano. For this reason we stayed near the Termini and then walked to the station. Once there I decided to just get the car there. The signage in Rome to the autostrada was not very good, but we managed. We took a train from Chiusi for a daytrip to Florence. Getting to and from the station is quite easy if you are going to that part of Tuscany. If you cansider this option by overniting in Rome I can give you the name of the very quiet and resonable b and b we stayed at near the station in Rome. Be sure and visit lovely Pienza for a sunset.