I'd avoid the clover if it were me. As for amending the adobe/clay soil and preventing weed growth consider these options. Try a layer of corn gluten meal on the recently scratched surface to inhibit weed germination. If you own a pickup truck, go out to a rock/landscape supply location and pick up a yard of 1/4 minus gravel. Not pea-gravel -- quarter minus. Work this into the top 4-6 inches of soil and then use 2-3 inches as a top dressing/mulch. This will areate the heavy clay and suppress weeds to the point where you can easily scratch out the few that manage to pop up.

Remember that the corn gluten meal will inhibit germination of new seeds (including ones you want to sprout) but will not do diddly to established weeds except perhaps help them along...so don't use it if you plan on planting new seeds in that place. The tiny gravel is really the key. I use it all over as a mulch/amendment/top dressing medium and it is the best. Grasses love it.

Arroyo, I cover the ground around my OG's with grass clippings. It not only keeps weeds down but also adds humus to my soil. just a suggestion..
I have planted clover and love it, but so do the rabbits and the deer. It also adds to the soil but be prepared for it to attract other things.

I'd avoid any nitrogen-fixing groundcover around OG's, at least the warm-season grasses. Excessive nitrogen doesn't agree with them. I like the fine gravel idea, and maybe even coarse sand. It maximizes drainage, keeping excess moisture at bay, and will diminish at least, the germination possibilities for weeds.