Believe it or not there are many people in South Texas and Northeastern Mexico with Irish ancestors. I know this because of this regions rich history and the names that I occasionally come across on the church and civil indexes.
On the 8th of January Chris Paton made me aware through Google+ about Irish Lives Remembered a Genealogy Community and its free magazine.
I already downloaded two issues and they are great. Even if you don’t have Irish ancestors I recommend you read them since it is always helpful to see whats available and the stories are great.
You can visit this website here http://irishlivesremembered.com/magazines.html and can read more about the Irish in Mexico at wikipidia http://en.wikipedia.org/wiki/Irish_immigration_to_Mexico.
Have fun and enjoy!