Our info is from 2004, so it's a little dated:
Montelfalco: we did not find any fine dining. We ate at Ringhiera Umbria in town. Quaint place for pizza and the owner is talkative.
Spoletto: great lunch at Il Tartufo. We killed a bottle of wine and sat there for about 2 hours. My memory is that there were only about 6 people there for lunch. Recommend.
You may enjoy going to Gubbio, a hill town. We ate at Taverna del Lupo as it was recommended to us, but I do not recommend it. It was a tourist trap with overpriced food and wine.
Trevi is quaint for a short visit and walk.
Torgiano has the wine and olive oil museum there.
Southern Tuscany. Don't limit yourself to Umbria. It's not that bad a drive in the south. (In fact, I never had a problem driving in Tuscany).
Montalcino - Go to the Castle. My memory is that Jcocktosten was there too and there is a wine bar. You can also drive out of town and drop in and visit Banfi without an appointment. I believe that they have a decent restaurant there too. You may need reservations.
Montepulciano: lunch or dinner at Le Logge di Vignola. One of the best meals of our trip (also expensive). Highly recommend.