I have black mold growing on my outside cinder block wall sourendering my back yard. I live in Las Vegas so the climate is dry but watering the lawns is causing the mold to grow since we have to water in the evenings so the water does evaporate so fast due to the hot climate. How do I remove this without having to sand blast which I have been told I would have to do? I would like to do this myself without having to hire a contractor.

If you sand blast you won't have any cinderblock wall left. The best thing to do is scrub it off with a scrub brush and a bleach solution.

First, make sure it is mold or mildew and not something else.
Using bleach, (1 pt bleach to 5 parts water) spray a small section.

If it is mold or mildew, it should change color from black. If it stays black, try adding a bit of dishwashing liquid to the bleach mixture, spray it again and then scrub it with a stiff brush. If it comes off with scrubing, then it is probably just dirt.

If this doesn't do the trick, you have a different problem. Do you notice this stain anyplace else that you water (sidwalk, house siding, car, etc)? Is it only seen in an area service by one sprinkler? (Assuming you have an in ground sprinkler system) Do your neighbors have a similar problem? There may be an issue with your water.

I just can't imagine how mold would grow in your climate from watering. The only way that I could see it would be if the area doesn't get any sun, and it is constantly wet (no water, no mold).

Good Luck, Dan