This is my new idea. I could get some sagebrush (a very natural plant around
here) and use purslane as a ground cover.

Sagebrush and similar shrubs are pretty flammable - are wildfires a
concern where you are? If so, they should not be located anywhere near
the house or any other structures.

I also have a much bigger section I'd
like things to grow in along the house (where I'm thinking of using the
prickly pear)..

Look around to see how prickly pear grows in your area. If it gets
weedy, it could be real torture to get rid of it or even to keep it
under control. Possibly a liability issue too. Or - consider buying a
completely thornless variety. For a bonus - get a thornless variety that
makes really good fruit!

cheers,

Marj
--
Marj Tiefert: http://www.mindspring.com/~mtiefert/
Mediterranean Garden Advice and Shop: http://stores.tiefert.com/garden/
In Sunset zone 14-mild