Fremont Peak State Park is south of the village of San Juan Bautista at 36 46 north, 121 30 west.
From Hwy. 101, about 11 miles south of Gilroy, take the eastbound Hwy. 156 exit. Go 3.0 miles, to a traffic light, and turn right onto county Hwy. G-1 (San Juan Canyon Road). After 200 yards or so the road forks, take the left fork. It then immediately forks again, this time go right. You should see a small brown sign saying "Fremont Peak State Park 11 miles." The road follows up the canyon and the winds up a ridge into the park.
The park charges a small fee for day or night use payable in any of several drop-boxes.
There are several areas within the park used by astronomers. See the detail map The Observatory is the contact point for SJAA activities at Fremont Peak. Check in there to find out who and where to meet. But note that only FPOA members are allowed to setup behind the ranger's house or next to the observatory. (In all cases, please be careful with your headlights.)