in the Dolomites the lifts are lifts typical a mountain town would have and there is no public transit system to speak of. There is bus service but a car gives freedom to see much more.
mreynolds I respectfully disagree. Every hotel, B/B, and apartment in the Val Gardena provides guests with a bus pass for the duration of their visit. This is in an attempt to keep cars off the road adn make everything run smoothly. The buses take you to any of the lift stations in the 3 villages and all the way up to the Passo Sella -- beyond it if you desire -- and cover all the way to Bolzano. We have been going there each year since 2012 and never have had a vehicle. We take a bus or taxi from Bolzano to the village, then use the buses. Even people who drive there park their cars much of the time and use the very convenient buses. You cannot even drive in the Alpe di Siusi unless you are staying there and even then it is restricted.
The Val Gardena is a paradise for hiking of any level from super easy to doing a via ferrata. I have to say its popularity has grown enormously in the past few years so I hope it is not impacted as horribly as the Cinque Terre. Cars won't help, but at least there aren't any cruise ships.
Look also at the Alta Badia and if you really want to have a car, check out the area near Moso in the Sesto Dolomiti. Great hiking, less patronized by North Americans, and a car really helps there.