This is nearly a P&G at the Panorama Nature Preserve in Fullerton.
A few months ago I went on a short hike here with Godzilla! and trekkerdmc. I had used up all my containers earlier on the walk around the neighborhood, but we realized that a hide-a-key could go on the preserve sign. I finally brought a couple containers by today, and decided I liked a different spot using a different container better. You’ll have to venture a few feet into the preserve, but you won’t have to leave the trail or take anything apart. I.e., it is not under a fence cap or in a rail; leave the fence alone.
After you’ve found the cache, continue up the hill for some very nice views of the surrounding area and the mountains. Provided it isn’t cloudy or smoggy, of course! Preserve hours are 7am to sunset, and parking is available on the north side of Ladera Vista Dr. during the same time period.