This is the Master Gardeners' Garden of the Seven Sisters. There are 15 plots to showcase sustainable gardening techniques. They hold demonstrations a couple times a month, but even when closed, it's still a nice place to gaze at the garden through the fence (and find a cache!).
Note: you may access this cache any time of the day, but watch out for muggles during events. Parking is available in the bordering lot, or on Sierra Way. There is no parking on Johnson Ave (I don't think).
TOTT would be helpful here. Bring your own pen.