If you want a low grower, how about lantana or maybe rose trained on a trellis or even pyracantha espellared (sp?)

Start in the early fall with cat's claw or other heat-tolerant vines. By next summer they may be established enough (and covering enough of the wall) to survive.

Or, how about painting a mural?

I agree with lazygardens. Key is Fall planting to get established before Spring/ Summer heat. Narrow trunked palms, such as Queen palm would work well too, but they will need supplemental palm food periodically (containing Mg, Mn) to avoid yellowing. I would wait it out until Fall....... not much will establish in mid Summer in Mesa.