Regarding frost protection for California... I'm from Florida so I know what
you are dealing with is different from say Tennessee, where I am now. Most
of the time Florida will have a simple convection frost, not too cold. The
warmth from the ground will keep everything above freezing under a cloth,
and there is no danger of the cloth itself freezing the leaves underneath.
Even when that happens here, it's only the few leaves actually touching the
cloth, not that big a deal. Your soil is not likely to get so cold in most
freezes that you have to worry about the cloth freezing. Plastic is another
matter altogether, it will freeze whatever it touches.
The trouble with Florida, and here for that matter, is when you get a
front that blows in and keeps on blowing as the temp drops below freezing.
That makes it very hard to protect anything above about a foot tall, and it
means far more damage than the temps alone, because of leaf dessication.
Donna