"Mexican architecture" includes a vast array of building types and styles from a period over a thousand years long. Before Columbus there were several different cultural centers with their own ways of building...including Mixtec, Zapotec, Mayan, Olmec, Teotihuacan, and last the Aztecs of Tenochtitlan. Spain began by demolishing or building over some of the older temples and erecting architecture in whatever style was current in Spain at the time, so that the architecture of Cortez' house in Coyoacan is quite different from the later churrigueresque churches. By the time Mexico became an independent nation, there were many variations of historical and regional types, all modified from the origianl sources by distance and local technology.
In this century, Mexico has several variations on Modernism, including stripped classicism, a particularly elegant "moderne" and a restrained variant of art nouveaus, not to mention the obvious international style work. The best known Mexican architect of the moment is Ricardo Legorreta, who recently completed the new cathedral of Managua, Nicaragua, as well as our new public library here in San Antonio. Actually, Arq. Legorreta would agree with me that his work owes much to the master Luis Barragan.
Because Mexico is such a diverse country, there is naturally a diversity of architecture. An example is flat roofs, shed roofs, gables with or without overhangs at the end walls, barrel vaults, domes, etc.
Any good university library will have books on Mexican architecture. There is of course a lovely book called "Casa Mexicana" (I think it is by Tim Street-Porter) about Mexican houses. You can also look up Legorreta, Barragan, Enrique Norten, or any of the earlier styles in Mexico.