If you are in the low desert the west side of a house with reflected heat is a brutal area to grow anything. A couple of suggestions from the Arizona Municipal Water Users Association's Landscape Plants for the Arizona Desert publication (free) are Desert marigold (Baileya multiradiata) and Candelilla (Euphorbia antisyphilitica).

Fun discussion! I love JonC's suggestions a lot. You could also get away with some of the super low growing Daleas too. I have some Agave americana plants surrounded by sandpaper verbena and they're all on the same watering schedule ("schedule" sounds fancy, it's me slopping water on them every ten days or when I remember) and they've all done great. The only downside to the verbena is that it needs hacking back now and then, and can get some frost damage, and the leaves ARE annoyingly rough when they're dry. Portulacaria would like the same conditions too, although it get get zorched by a hard freeze.

I'm sure others will chime in with suggestions too. Let us know what you pick and how it works out. If nothing else, some low-growing Echinopsis cacti would work too.

Fun decision, keep us posted! Happy gardening!
Grant

Jon, desert marigold and candelilla sound wonderful. I'm in Tucson, so I'm not as low desert as Phx or Yuma, but yes this spot with the agave is a bit brutal.

Portulacaria is an intriguing idea. It's a small area close to the front door and would be easy to throw a blanket over on nights when hard freezes are expected. I'll have to look into that. And as much as I'd like to avoid lots of spines, I might have to tuck a couple of torch cacti in there, love the flowers.

Thanks guys!