We are studying contemporary Latin America this year for social studies using Rod & Staff's Understanding Latin America(sixth grade). The first unit covers Mexico. Here are a few free printables referencing Mexico. These resources are very old, vintage textbooks from public domain; however, they are still relevant for the study of the history, cultural influences, and geography of Mexico. All are in public domain, and are free to print or download.
Our American Neighbors by Fanny E. Coe: Mexico
An Easy Introduction to the Study of Geography: Texas and Mexico
The Fifth Reader: Mexico as First Seen by the Spaniards
The World and Its People: A Bird's-Eye View of Mexico
Old World Background to American History: Spanish Conquests in America
Story Hour Readings: Storming the Temple of Mexico
School Reading by Grades: Sixth Year, How Cortez Entered the City of Mexico.
The Guyot Geographical Reader and Primer: The Warm Countries of the South.
I didn't add this one to our reading because it was a little much for my eleven year old, but I couldn't help chuckling at this portrayal from A Child's History of Spain(1894):
"In these temples, which were called Teocallis, prisoners of war were sacrificed to the Mexican gods, and their flesh eaten by the chiefs and priests. The victim was led to the top of the Teocalli, where he could be seen from afar, was laid on a convex slab of stone, and held there by five priests, while a sixth cut open his breast with a sharp knife of itxli, and tore out his quivering heart. There were hundreds of such Teocallis in the cities of Mexico, and thousands of such victims sacrificed in them every year.
Manuel in Mexico
Roy and Ray in Mexico
New Geographies: Countries South of the United States
Map Studies of Mexico
Heroism of Boyhood: Heroic Devotion of Two Mexican Youth
Viva La Mexico!