In Edinburg, Terra Preta Farm is a "family farm serving the Rio Grande Valley area. They grow organic vegetables, fruits, herbs, and flowers". Juan, Shakera, Little Shake, Kanani, and Andres are the family members that manage it. Although they opened for business in November of 2011, they have been in agriculture since 1996. Moreover, they "see soil fertility as the core of successful organic farming", and that's why they work hard in keeping their soil very active and full of minerals. Also, they are offering weekly and biweekly vegetable shares. Check them out at McAllen Farmers' Market on Saturdays from 10 am to 1 pm.
They haven't updated their CSA page since October 2014, contact them directly for more information.