While I am interested in the towns I am more interested in the countryside of Tuscany/Umbria. Is it possible to wander the countryside or is it only possible to drive through it?
Nick - It really is a matter of time. Sure you can "wander" - but are you using your time effectively. Trains are OK but to really see Tuscany and explore it you need a car. Also remember that they are called "hill" towns for a reason. Lots of steep hills. Last time I was there in the summer I felt sorry for the bicycle tourists sweating it out trying to climb up to the villages.
Have fun on your journey!
See "Walking and Eating in Tuscany and Umbria" (e.g., at Amazon http://www.amazon.com/Walking-Eating-Tuscany-Umbria-Lasdun/dp/0140264604/ref=sr_1_1/105-3344480-9599653?ie=UTF8&s=books&qid=1179528392&sr=1-1)
Lots of great walks with specific directions for traversing private lands (which is apparently legal and acceptable).
I think you would enjoy a car....Trust me....you will wander when in a car...as it is easy to get lost......we did and never made it to the town we wanted, but found some other charmng towns! We just wandered around, looking for interesting palces...We stayed in Umbria on the Tuscany border by Cortona......Marilee