While on vacation I spotted a car with California license plates and a frame around the rear plate that said "Fairview Ford, San Bernardino". Wasn't Fairview the name of one of the schools in the area, along with Westdale? Granted, San Bernardino is towards the mountains, but still ...

Yes, those were the correct school names.

Judging from their proximity to the beach and the movie studios and the suburban look of their neighborhood, the Bradys apparently lived in the San Fernando Valley (Also, the outside shots of the Brady house are from an actual house in Studio City).

The most recent Brady TV movie on Fox said they lived in Santa Monica, but that movie was a parody and not part of the series timeline, so my best guess would still be the Valley.