Ask Mr. Smarty Plants

What you are probably seeing is Solanum elaeagnifolium (Silverleaf nightshade) a common plant you would see in your area. You have made it easily to identify with your clues of five petaled lavender flowers with bright yellow stamen. In the Solanaceae or potato family, five petals fusing to form the flower are a common trait and nightshade has this distinctive coloring of purple and yellow. 

In El Paso and throughout the Southwest there is a long history with nightshade in the making of cheese, specifically Asadero cheese. The crushed seeds from the berries helps to curdle milk. These berries are poisonous to people as well as livestock so don't attempt any cheese making yourself. It also produces solasodine, used in the manufacture of steroidal hormones. Medicinally it has been used for tooth aches, sore throats and even rattlesnake bites. 

Nightshade is a perennial. The roots are long, sometimes up to six feet, which is why you notice this plant in higher numbers than other flowering plants in times of drought. They also produce rhizomes which help to keep the number of plants plentiful once established. Silverleaf nightshade is considered a noxious weed throughout the Northwest. States in non-native regions where it has been introduced find it hard to eradicate. Nightshade is highly deer resistant, so for your area, it is not a bad little plant to have around.