My husband and I drove through the Monti Sibillini national park as part of our week-long trip to Umbria in October 2011. We stayed in Torgiano, a small village just outside Perugia, and spent roughly 6 hours driving through southeastern Umbria. Here are our tips for visiting the park, including the cities of Norcia, Casteluccio, and Visso.
The southern highway into Monti Sibillini runs between Spoleto and Norcia, and is a scenic and easy way to see the park. Along the way, you can stop at one of the many adorable tiny towns - we stopped at one of the salami shops in the town of Serravalle (which offers white water rafting) and were treated to a wonderful tasting of the different types of salamis (fegato [liver], cinghiale [boar], cervo [pork]) and cheeses (pecorino duro [hard pecorino, good bite to it], semi-duro, ricotta salata [specialty of the region] and formaggio fresco [great on sandwiches, nice soft cheese]).
Norcia can be seen in a few short hours (or days, depending on your schedule). The alleged birthplace of St. Benedict, the small town offers picturesque views of the surrounding mountains and great local fare for a quick lunch. We ate at a restaurant that was off the main plaza (the one on the plaza seemed a bit touristy), full of locals. We recommend the grilled pork platter!
After Norcia, we headed north to Casteluccio, a MUST SEE for anyone traveling through Umbria. Casteluccio is a small hilltop town located in the middle of a vast, high plain in Monti Sibillini, whose plains flower in late June to early July for some of the most breathtaking colors on earth. You should park first, then take a brief stroll through the tiny town, as the streets are difficult to navigate (we had an interesting time turning around on streets that were at a 40 degree slope with nothing but a sheer drop!).
After a nice stretch walking through Casteluccio (which is thankfully being restored), we then took the northern road that passes through Visso on the way back to Perugia. Worth the drive.
The entire trip took 6-7 hours, and the roads were well-marked. I would recommend travelers avoid driving at night, as the roads wind through some fairly high mountains and are not lit.
We didn't make it to some of the waterfalls in the park, and we wish we'd planned ahead before heading out. My understanding is there are several accessible water falls not too far from where we were.