Engines often run at roughly 200 degrees Farenheit. California may be warm, but it's not that warm. Thus, a cold start is still a mileage hit since the engine and oil are only at 70 degrees initially. Actually the HCH suffers more from a cold start than a Prius because it will not auto-stop until the engine is at operating temperature (and sometimes not even then).

Anyway I live in San Diego and you can see my lifetime mileage over 12400 miles in the 2006 Civic Hybrid I just sold. Note that while I do drive 80 mph on the highway, I still try to drive somewhat gently, including coasting where I can, cruising at a fixed speed instead of varying my speed often, etc. Anyway tanks that were largely composed of highway driving net me around 42 mpg (like if I drive to LA and back), but my overall mileage is worse because non-highway driving (or stop-and-go driving) result in worse mileage.

Driving on I-8 from San Diego to El Centro and back results in 40-41 mpg. I mention that because it's a large uphill climb (to 4200 ft I think) each way. The car gets 30-31 mpg on the uphill segment but that goes up to 40-41 by the time it reaches the bottom again.

A Prius is more efficient in addition to being faster, but I personally don't like them for other reasons.