Well, it looks like the casa and the grounds fit right into the surrounding landscape. So, I'd just enhance and extend that natural look, wouldn't try to go against mother nature down there, just go with the flow. Layout some beds around the house for those no-fuss, blooming cactus plants and some of the greener ones, stagger the height and texture. Build one of those great outdoor fireplaces with some comfortable lounge chairs in a teak or redwood, put some good pads on them with heavy duty fabric so you can sit back and enjoy the millions of stars in the nighttime sky and the moonlight over the water.
Can't tell much about the house from that photo, but I'd probably continue the natural look inside as well. Keep it low maintainence. It would be helpful to know what the floorplan looks like :)