Now, the term "wandering" can get thrown around as a negative comment for a writer who really doesn't know where his story is going. That's not what we mean here. Anaya knows exactly where he wants this story to go, but he's going to take one heck of a route to get there.
Anaya's not afraid to let the story wander down strange paths and take a few side trips along his way. Those often come in the form of Antonio's ponderings, wonderings, and preguntas. He veers from idea to idea, and we can only roll with the punches. For example, thinking about forgiveness can lead him to recount a story of the past about the boy who saw the Virgin of Guadalupe, which somehow—just trust him—relates:
My mother had told me the story of the Mexican man, Diego, who had seen la Virgen de Guadalupe in Mexico. She had appeared to him and spoken to him, and She had given him a sign. (16.43-46)
This might sound like the stock and standard attention span issues that many young boys face, but it's more than that. Antonio is just really good at looking at all sides of a situation, especially when that situation doesn't have a clear right answer. He likes to come at things from different angles—it makes for a better view.
Wandering in and out of past tales is mirrored in the literal journeys that Antonio takes throughout the novel. Anaya sends him to his mother's family's house multiple times and to the Téllez home, and off to school and back. While Antonio definitely moves forward as far as growing up throughout the novel, he doesn't necessarily move in a straight line toward that end. He doesn't gain an answer and then move on to another question. He keeps wandering and seeking and coming back to the same questions over and over. It could drive a lesser kid crazy, but Antonio makes it work for him.