Just another newbie here, I am in LA as well, planning for a very small garden coming up soon. We have some unique issues here in LA, and the first is where's the rain!!! will we ever get any more??? and til then planning low water vegie gardens.
I recently found a website of an aussie gardener, in a hot dry area of australia, who did large lasagne type beds, using straw bales as the walls.
With all the mulch, he uses very little water, and does pretty well.
If you did something like this, you could just leave the debris buried in the soil,
eventually the beds would become topsoil.

yep, it's been dry...we do live in a desert region, a reason that i focus on the plants native to this zone and do not focus on tropical plantings.

anyways, that is the plan for us for the areas in which i did the sheet mulch method, to let the materials decompos into the soil. however the site is too large to do this everywhere, too much material to bring in. also we are planting all drought tolerants and natives, but the current acidic soil does not support these plant types, thus the ammendments.

First, how do you know the soil you have is acidic? What did a good, reliable soil test say the soils pH was?
Soils in California tend more toward alkalin, sodic clay because of the low rainfall instead of acidic.

yes i was surprised. the soil is a 5.9...it's high in metals such as aluminum, zinc and copper, there's also lead, cadmium, and other nasty stuff (i was told to keep the soil wet so as not to breath in the dust, i wear a mask as well). it's also hydrophobic so it's difficult to wet. in order to grow native and drought tolerants i'll need to incorporate good organic material, as well as neutralize the pH. oh, and raised beds for any edibles.