Chino Hills State Park has a campground with a small number of spots. These hills are amazing after a good rain. This year it was a good place to see the wildflowers. Unfortunately the campground has been closed for awhile due to water line construction but should open in December 2019.  There's plenty of restrooms and parking. There's also a number of hiking trails that leave from the campground.  The only cell service is on top of the closest hill.  Its a good spot for a quick getaway from the city.