Were can they go? Depends on how big your tires are and if you pay any attention to those signs that say " No carts past this point"
You can take them on any of the paved roads, There is parking by the Camp fire area and both pools. There are also "parking lots" at the beach, outpost, settlement bus stop, and both trading posts.
Basicly the Fort is designed to drive a cart or take the bus everywhere. They really don't want you to drive your cars since there are no Car parking anywhere.
2 years ago my mother drove one down the service road to WL and parked under the huge valet area. Nobody said anything to her, but I would not recommend trying it.