I was trying to identify specifically what these tiny little flowers are and I think Chris Rowell of Newbury Park correctly nailed it down to California Goldfields (Lasthenia californica). These ones are seen adjacent to the fence on the west side of the park that lies adjacent to the Las Virgenes Reservoir.
If you do visit, like with other wildflowers, please do your best to enjoy them without trampling on them. That way we can all enjoy them each year! :)
The Stagecoach Trail at Wildwood Park also has a patch of these pretty yellow flowers.