There is a 'Wilderness Access Day Limestone Canyon' Sat 1/9. The access is from Santiago Canyon rd. and the ride is more or less on the on the Loma Ridge above Orchard Hills area. I have been on Docent lead rides in this area and its nice, you can ride in limestone canyon and there's a trail that connects to Mustard Road in Whiting Ranch. Looks like plenty of spots left.

Keep looking on the link for Orchard Hills events, its very nice in there. You can relax at Peets (Culver & Portola) after .

http://www.irlandmarks.org/Activities/default.aspx