You can never, especially in the desert, give your garden too much organic material. Not only will the organic material add to the soil's fertility, but it will also help it retain moisture, which, again, in the desert is a high priority. So plant the cover crops, or go to the nurseries and buy bales of peat moss or bags of compost and dump them out onto the ground. If you can't afford peat moss or compost or even bags of cow manure, don't despair. You can fill the garden with loads of organic material and do it for free.
Leaves are one of the easiest and most overlooked ways of adding organic material to the garden.
Rake the things up and put them on the garden. Go up and down the street and take the bags of leaves sitting on the curbs and throw them on the garden. Get as many leaves as you can. You won't be sorry. Fall Planting Fall is also the time for planting some of next year's root crops, especially garlic.