Not certain about the exact tolerances of these plants, but I've frequently seen poppies and black eyed susans, particularly the former, on highway medians. Maybe you could take cues from the plants naturally growing alongside the roads in your area. In any event, you're doing a great project -- best to you!

Look at the "inferno strip' plants recommended by High Country Gardens. Tough as nails plants for hot, dry strips.

Black-eyed susans and purple cone flowers seem to do well in those situations here, and I think they are native there.

Ziggy