Look, to the correct point, it is not. It should be:
Oramos para Monterrey y todo el Mexico. <------- This is a transliteration of We Pray for Monterey and all of Mexico.
Who/what exactly are you pointing this letter to? If something happened in those places (bombing or terrorism), then it should be like this:
Oramos para Monterrey y todos en Mexico. <------ That means you're referring to people/habitants.