What is the theme in Caramelo, or, Puro Cuento: A Novel by Sandra Cisneros?

What it Means to be Mexican is a theme in the story. There is so much reference to skin color, language fluency, family, and point of origin that the average person has to ask "What is a real Mexican?" Is it the person from Mexico City, cultured with just enough Indian blood to never forget the tragedies that ensued, but Spanish enough to not show the Indian that exists? Or is the Mexican in the north, close to the border that eats the flour tortillas instead of the corn tortillas eaten in the middle and southern states?