Starting today, Thursday, January 15, 2015, citizens of Mexico can obtain certified copies of their birth certificates from within the United States. The birth certificates are available at Mexican consulates around the U.S. Mexican citizens will need to present an official identity document, their Population Number (CURP), and pay $13 per certificate.
The nearest Mexican consulate to Nashville is in Atlanta, and the consulate makes frequent trips to Nashville for the mobile consulate. See the announcement here.