Here are 3 poss. starts for a GMR climb, I've used two: the lone hills center (pizza place there) and at equestrian center at the base of the climb and parked in the tract across the street, but wonder if it might be posted closed being adjacent to the course.

Looked at the map, there's a school just west and south off N. Loraine- Sellers School.

Start time depends on destination, the switchbacks of the final ascent or GRR?