Judging by the trees, this does not look like the south facing scrub foothills portion of the Angeles.
ANF - Wild Trout on Vimeo
ANF - Wild Trout on Vimeo
I think I know where you're talking about. If you remember, don't post the name. A few of us have been there. It went through a real tough period with drought followed by flash flooding, and is hopefully in recovery mode.Back in the 70's, I would drive into the San Bernardino mountains east of LA and fish the streams. I can't remember the name of the stream. Used to have a blast catching rainbows. Nothing big - maybe up to a foot long. Once you go upriver a quarter mile or so, the fishing would really pick up.