There's not a lot between Princetown and Bellever except tussocky moorland and chewed up farmland. I certainly wouldn't be heading that way myself, however it,s your ride and I'm sure you know what you're doing.
I'm yet to ride with anyone who didn't either enjoy it or refuse to ride it, so it's definately worth a look if you're in the area. In my experience it's best approached from the path that runs N-S at the trail junction at SX646 772, keep to the left and don't head up to the tor. Keep going south for 500m first climbing then a nice bouldery descent and you'll find the top of the rock garden on your left at SX 647 764. As shinythings has said, there is a trail from the top of the tor and that looks fun but I'm yet to try it myself so I can't really give any directions.
There are some other excellent trails in the forest including the long descent running east from the trail junction at SX646 772 and drops down to the YHA at Bellever.Access this by turning left at the bottom of BRG and climbing up the fire road.