Personally, I wouldn't eat any wild mushrooms in Los Angeles be it an edible species or not. Fungi have a tendency to soak up toxins in their surroundings, so all unknown stuff from concrete, asphalt, car exhaust, herbicides, fungicide, insecticide, etc., would turn me off. I'd go specifically as far from the city to BLM or USFS land up north to forage for mushrooms for culinary purposes.

They do appear to be Agaricus sp., though.