Follow this road to the end, turn right, then turn left to find
a little-known entrance to Rancho San Antonio. (I could not place
this cache any closer due to several invisible puzzle caches in the
area.)
I was in the area exploring the Mary Stutz Path (GCK97T) and
checking out the nearby "shacks" and the beautiful Quarry Lake (and
thinking about buying some Lottery Tickets so I could live here
too), when I noticed this familiar brown sign! Could this be a back
way into Rancho San Antonio? A passing pedestrian confirmed my
suspicion and I planned a return trip. (Note that the paper
Pathways Map, available at the LAH City Hall confirms this as a
public easement trail.

After some satellite reconnaissance at my computer, I saw that
indeed there's a clear road from here up to the Chamise Trail. It's
a steep, but short walk, that does not involve any trespassing,
though there are some small signs on the way down indicating it's
not an official trail (though it's big enough to drive on!).
Parking near this trail entrance is plentiful, unlike Rhus Ridge
and Mora Drive entrances. On a weekday morning there were 2 other
cars parked here. plus a neighbor jogging with his dog, enjoying
this area.
FYI: The empty building lot at the north edge of the lake is
currently for sale @ $2.75M and the houses on either side of that
lot are about $5M each, according to Zillow.com. Ouch!