Los Penasquitos Ranch House, at the start of Los Penasquitos Canyon Trail, is an old fashion place that I like to revisit. While I was waiting for the kid to finish the baseball game, I spent a little time over there. Seems an interesting place. The hiking trail is also a good one.
Another place, Mission Trails Regional Park, http://www.mtrp.org/, much bigger area than I thought. View is also beautiful. Only spent very little time during the weekend, certainly a good place to explore later.