If you plan on doing "major landscaping" within the year, then I probably wouldn't bother with the expense and effort to do a quick cosmetic fix. Without a functioning irrigation system, you will need to be out there on a routine basis. And lacking that, any plantings will struggle and fail.

In the meantime, find a garden designer experienced with 'California Friendly' (aka drought tolerant/water-wise and fire resistant) landscape design and plant selection. Once a well-conceived design plan has been formulated - and that can take some time - then you can focus on amending and repairing the irrigation to match. And in your climate, an earlier season planting (like spring) is more desirable than waiting until summer or even fall. Winter works well, too.

If you are unfamiliar with the plants suited to your area, a good designer is invaluable with both plant selection and placement. And you can do the installation work yourself to save money.

Try some succulents. If you have friends who have some, you can beg, borrow (or steal, I suppose) pups from them. You can even just plant them in planters and move them around later. There are aloes and agaves (and others) that can be large and attractive. Go to the Huntington Gardens and check out theirs. They are amazing.

https://www.gardendesign.com/succulents/huntington-botanical.html

I second the idea of planting succulents, and mulching with decorative gravel (not organic mulch). Instead of spending the money on installing an irrigation system and water bills, spend it on agaves, cactus, aloes, yuccas, small palms and flowering shrubs native to California.

Water-wise gardens can be surprisingly green and luscious. If the landscape below can be done in Arizona...

(Sorry don't know whom to credit)

Firesticks always catches the eye...wherever its put,it stands out. Blue Senecio under it is classic.

You could go natives..but then you really need to research that. Native does not mean easy.

I find liriope invasive. Lantana is great. Don’t use gravel because if you don’t want it in the re-landscape....too bad. Whatever you plant will need some water, don’t forget.

“I'm that guy who can't keep a house plant alive”

Luckily keeping plants happy outdoors is generally far easier than inside. Indoors they’re totally reliant on you. Outside they are freer to make their own way, whatever you do or don’t do.