The 20th Annual Tejano-Conjunto Music Festival will take place at Rosedale Park in San Antonio, May 13th - 15th, 2011. 

For more information on the Tejano / Conjunto Festival, contact the Guadalupe Cultural Arts Center, San Antonio, Texas at (210)351-7787. Individual tickets are $7 per night, and an "All Events Pass" is available for only $30 (which I think is the better value).