New garden, new gardener

Hi friends! I'm a new gardener; I have propagated a couple of easy plants (succulents, purple heart, grocery store potatoes and celery) and I have a (small) container vegetable garden. I am very inexperienced when it comes to putting things in the ground and growing from there.

Very soon I'm going to be long-term renting from a family member who says I have free run of the yard. It's a quarter acre property, about half of which is plantable (there's a lot of poured concrete and a long back yard).

I know it's probably too late in the season to get anything new started, but I am looking for some advice on what to do to get the yard ready to be a garden in the spring. I want to primarily plant vegetables and buffer plants but I would love some fruit trees - this is part of southern California that used to be an orchard and there are still citrus trees all around the neighborhood.

At the moment the yard is a lot of weeds and some pretty poor soil with no sprinkler system in an area in the middle of a drought. I've got ample room for composting, a few fire ant mounds, not a lot of shade, and (so far) a good attitude.

Can I get some tips on what I can do to enrich soil, get rid of weeds, deal with fire ants (Are they secretly beneficial as pollinators or something? Do they eat worse pests? Should I tolerate them? Should I eradicate them?) and generally prepare a big space for next spring?

Thank you so much!