Call a bulk propane provider that delivers to large tanks like 300 gallon, 500 gallon or 1,000 gallon. This is who will give you best pricing.
See other GJ threads on this same topic as you will want to BUY YOUR OWN propane tank as it will give you lowest cost in long-run.
Also, you'll want to fill your propane tank in "off season" which in cold environments is the summer. Hopefully that is also true in California that you can get best price in summer. Thus, you'll spend a lot of money all at one time, but overall it will be cheaper.
Finally, plan out buried underground yellow polyethlene plastic pipe from tank to house, and tank to garage, and one of these T off to a BBQ grill so you won't have to mess with 20 lb bottles.