From Hwy. 101 or Hwy. 680 take the Alum Rock Ave exit east. 2.2 miles from 680 turn right (south) on Mt.Hamilton Rd. (Hwy. 130) and go 7.7 miles to the park, on the right. (Mt. Hamilton (Lick Observatory) is 11 miles farther.)
If you're starting from south of 280, take the Tully Road east exit from Hwy. 101. Turn right on Quimby Road which curves around Eastridge Shopping Center. Continue over the hill and back down (about 6.5 miles). Turn right on Mt. Hamilton Road. Grant Ranch is on the right just 0.2 mile from the intersection.
After entering to park follow the main road to the tee; turn left into the parking area where the observing session is held.
There is a $2 fee.
Note that the park closes at sunset and you will not be able to get in at night except for officially scheduled events (usually organized by HVAG) or by special arrangement with the ranger.