Not an authority on Temecula, but am a native San Diegan who has also lived in many other places, so I’ll just interject a couple of thoughts here.
You have many valid questions and concerns, but you have to realize every location in the world, including the alternatives you have mentioned, have their pros and cons–just as SoCal does.
No place is perfect, so, in the final analysis, it will all boil down to getting the things you and your family want MOST. There will be a give and take with every location, and you probably need to spend time in all of them to make a good decision.
After living many places in the world, I can tell you that we would never permanently live any place other than San Diego. It ranks the #2 place most Americans would want to live in many polls, (NYC is #1) so, apparently, I’m not alone.