Sounds like your parents are still the partial beneficiaries of a true sweet spot in Southern Califorinia. At the time of Richard Henry Dana, the LA basin was not that nice a place to do more than raise a few cows and bemoan the lack of a local market. There wasn't enough water for even a small population until some water management was implemented. By the time the Owens Valley had been turned into a desert and the CA Colorado River Aquaduct had been built, Southern CA enterred an agricultural [and in many ways residential] sweet spot.

For the most part, the agricultural bonanza has been paved ... and suburbia has run amuk. It is still a great place for a lot of things, but population pressures have defined the highest use as near endless suburbia. [Oh well ... maybe in another lifetime or on mankind's next planet.]

BTW, for purposes of full disclosure, I have lived in LA County and it appears highly likely that I will do so again in the very near future [gasp / sigh / does anyone know a good pychologist in the Westwood / Santa Monica area?]

I would like to recommend the book "Extreme Simplicity: homesteading in the city" by Christopher & Dolores Lynn Nyerges. They live in the LA area, and have figured out how to homestead on their suburban lot. Lots of great ideas.