The water in San Diego is pretty terrible. And I don't think LA is much of an upgrade. It's not a California-wide thing; it's the luck of history that San Francisco built the water supply that it did when it did, and that several neighboring counties were able to tap into it as well. They wouldn't do it today (including damning the Hetch Hetchy--in fact there are people who advocate for removing the damn, but I don't think that will ever have legs, at least not in my lifetime).