My family made our annual camping trip to Del Valle Regional Park again this year. Our Friday morning was spent taking a pleasant walk along the Vallecitos Trail. The trailhead is right across the road from the campground entry kiosk. Alternatively you could connect to the Vallecitos trail from the Ohlone Regional trail.
Reception in the ravine wasn't great so you'll want to cross the creek bed from the trail near the large prominent boulder.
The initial cache contents include some kids toys and a couple of trackables.