Hello there,
I personally have not yet connected anyone from the many last names on my tree to Coahuila or Nuevo Leon.  About 90% of my family stayed in the 3 states, the other 10% went on to California and Chihuahua.
When you least expect it, you will find the link... don't give up :-)
For me, it usually happens in the middle of the night when I can't sleep and decide to try one more time.
Saludos,
Sandra Gómez Mendoza
San Antonio, TX