The billboard is in Hillsborough just south of where Rt 206 narrows to just 1 lane in each direction. It's right after a big nursery on your left as you are heading south. I was going to take a picture and post it but I'm out of town on vacation and didn't get around to it yet.
And the sign uses CR's formal name: Washington Valley Park.
I'm not sure how I feel about this as a Somerset County taxpayer, but at least it reaffirms the good relationship that the MTB community has with the Somerset County Parks Commission.