The Craner Canyon road

is beyond the "No trespassing" signs and just to the right of the "Enter Only" sign, visible down the road in this pic (go to higher resolution). You actually never enter the quarry when you reach the BLM road and don't worry about actually trespassing since you never do enter the quarry itself. However, if heavy equipment is being used in the area, be respectful and avoid getting in their way. Craner Peak is on the left in the background.