Lake Skinner (Riv Co Parks and Open Space District) and the surrounding property (SW Riv Co Multispecies Reserve) is off limits to all RC flying, as its a wildlife reserve.You can legally fly on Cleveland NF (Palomar) and San Bernardino NF lands (San Jacinto Mtn) lands, and there are parcels of BLM land on several of the open spaces around Temecula towards Hemet and Anza that are accessible too. If you are low key about it, there is a lot of open space hills between Menifee and Hemet that are only partially developed or abandoned development and they are unfenced (Southwest of the cross of Domenigoni Pkwy and Winchester) that may be ok and rhey are not within 5 miles of Hemet/Ryan airport. Also check out your local RC club flying fields- we have one in Hemet that has some guys flying drones too, but uou have to be a member.
I use mine on public forest and BLM lands mostly, and occasionally once or twice at random times over the local unfenced private fields in our area that don’t post “no trespassing” signs. If you are legally parked along public roadways, you’re not trespassing if just flying over a open field without landing in it. I have also been given permission to fly on private property East of Temecula just by offering to give the owner some free photos of their orchard and home ( I’m 107 permitted), but you wouldn’t be trying to promote a business doing rhatnif it is to just fly for fun. You can easily find someone willing to let you if you try.