-I can only give you what I would do, which is this:

set up a compost bin

rake up all the dead stuff and put it in the compost

pick a place to start - right by the deck, maybe, and work your way from one end to the other. Put pulled up plants/weeds in the compost and make a brush pile of the woody stuff.

get a tree company to cut down the dead trees and take the brush pile

mulch everything with wood chips, 3 inches thick or more.

take advil.

You are going to have to nibble away at this; everything is so overgrown that you can barely see what you have.

If you don't already have garden tools, get yourself some really good ones - nothing from Home Depot - and use gloves!

Thank you so much, we will see how many compost bins I can fill this weekend :)

I would do it differently. I would clean up the dead stuff, yes, but after that I would try to bring back to life what is already there.

The place looks dried up, so I would start with watering, infrequent, but deep and thorough, say once a week, may be even every five or six days, depending on the weather. You don't know what kind of green wonders may show up there, even after a month or two. I would wait a year or so before getting rid of anything. Only then I would select what I want to keep.

Mulching is a great idea, but only when you already know where to put it without smothering your plants.

And don't use a compost bin. Just put your garden refuse in the designated little spot in the corner of your garden.

You might want to post this on the California Gardening forum. Folks there have fantastic ideas and experience!