From what I understand, the greensand is a good tool for lowering the pH in the soil. You can also put 1 tablespoon of apple cider vinegar in a gallon of water then drench the soil to lower pH. Sulfur also lowers soil pH, but you need to be careful not to use too much. I believe 5 pounds per 1000 square feet is the most you should use. Cotton burr compost is more acidic, too.
The climate and the soil in San Angelo is also a factor.
Check out this site for more information:
http://attra.ncat.org/new_pubs/attra-pu ... l?id=Texas