In an op-ed in the Washington Post defending the Mexican cartoon of the black ape-boy Memin Pinguin, Mexican historian Enrique Krause writes:
Other famous leaders in Mexico's history were African American in their origins: Jose Maria Morelos, for instance, who became the second commander of the Mexican rebels in their War for Independence (1810-1821), and his immediate subordinate, Gen. Vicente Guerrero, who became president eight years after Mexico won its independence from Spain. In the 20th century, only two presidents were of pure-blooded Spanish descent (Jose Lopez Portillo and Vicente Fox). All the rest were mestizos, of mixed ancestry.
First, it would be remarkable indeed if two Presidents of Mexico were African Americans. In reality, Morelos and Guerrero were of part African descent, not African American. Second, Vicente Fox is not of pure-blooded Spanish descent, as his surname shows. His paternal grandfather was an Irish-American who was born in Cincinnati.
Overall, Krause is largely blowing smoke about Mexican attitudes toward race. They are quite different from American attitudes, and they are of increasing importance, but you won't find out much about what they are from the American press. My articles about Mexico are here.