I don't think you're going to find any flowers that will withstand that amount of summer sun while stuck in a bunch of rocks. I'd visit a nursery and ask for recommendations for drought and heat tolerant shrubs. Perhaps some Aussie native plants might work. And you might even get some color. Other than that, my only thought is plastic mums. ;O)

Hmm....fun question. It sounds like a good spot for aloes, like nice chubby upright Aloe vera, or low-growing spotted Aloe saponaria (Aloe maculata). If you have frequent automati drip irrigation there you could try the dwarf growing Katy ruellias (Ruellia, aka Mexican petunia), or even Asparagus fern (I grow plenty of that in full sun). If you like annuals you could try vincas, which is my go-to plant for summer flowers, or even lantana if you have irrigation and hack it back in late winter to keep it under control. I'm sure some others will have a few ideas.

Let us know what you try and how it works out. Good luck!
Grant

Here is a link that might be useful: Pics, so far, from my garden April 2012

Thanks for the tips. I'll look more into the Mex Petunia, vincas and lantana.

Any particular Aussie native plants?

I mentioned flowers, but by no means am I restricting myself to flowers, nor if they don't flower, so long as the plant remains green... anything green will work, but not desert type plants (cactus, etc.)

Thanks for the help.

I guess I'm not sure about your size. I'm thinking of some of the more desert-y flowers - Salvia leucantha (can get big), chocolate flowers, Gaillardia (which are coming in some nice cultivars these days).

I'm afraid I haven't lived in the desert in a long time, so I might be off on how well these survive the summers, but I think they'll make it...? Zinnias also did really well, as I remember.

Something else you might think about is some of the grasses - Muhlenbergia, Stipa tenuissima, some of the smaller (and sterile) Pennisetums - Pennisetum setaceum 'Cupreum' (check size on that one?) and P. rubrum - clumps, up to about 3'.

Other ideas:

Angelita Daisy
Rain Lilys (pink, white or apricot)
Golden Dyssodia

These are perennial - no replanting every year. ;-)

Well, I think I've decided on white vincas.. they're annual though since Lowes doesn't carry the perennial variety.

It's a start, and I'll see how they survive the summer. I may be planting a bit too late... but we'll see.

Thanks for the help.

Thanks for the update! Good luck and keep us posted. I've got several pots of vincas going in full hot sun and they look great, plus a big bed of them around a small tangerine tree and they look really good too. Hopefully yours will do well for you, they're good little performers through late autumn, and they should have blooms every single day through then, so quite a nice long display. Happy gardening!