Maples are forest trees, Japanese maples are forest understory trees. Los Angeles is "stinking desert". Not a good climate for trees that require humidity and light open shade. That is why you don't see maples in your part of California. Try growing desert trees and shrubs. You will have more success. A blooming palo verde tree is beautiful. Pomegranate does well in the dry climate of your area of california. Look through check lists of locally to your county native trees. Many will be useful for bonsai. Unless you can radically modify your environment, your area of Los Angels is too hot and too dry for Japanese maples.
Sorry, I am not intending to sound harsh, the "stinking desert" remark is my though after spending a lifetime one day stuck in Los Angeles traffic. I really was trying to be a little humorous.
Seriously. Climate is the reason. Best is to embrace what will grow in your climate. I get "Climate Zone Envy" on a regular basis. In the end, I have to resign myself to sticking with what will grow where I live.