California is 800 miles long, and the half you pick decides how many lessons you fly in a year. The state that appears in flight-school advertising — sunshine, coastline, mountains before lunch — is the southern half. The north is a different training climate with a real winter in it.
Within Southern California there is a second split that matters more. The coastal fields — Santa Monica, Torrance, Long Beach — sit under the marine layer and lose summer mornings to it. The inland valley fields — Van Nuys, Burbank, Whiteman — sit behind the hills and lose fewer. Thirteen days a year separate Van Nuys from Santa Monica in the study, almost all of it between June and August. What you gain inland you pay for in July heat and density altitude. Neither is a bad choice; they are different ones.
Our honest position on the rest of the state: if you live in Northern California, train in Northern California. Nobody should drive four hundred miles to a flight lesson. If you are comparing pilot schools in California from outside the basin, the questions are the same everywhere — instructor turnover, aircraft availability on a Saturday, whether the price is fixed, and what happens to it at hour forty-eight.