The $20
The $20 bill is a symbol for currency of course, but it is also a symbol for sacrifice, because, on a religious whim, he tries a Hail Mary, to use a football metaphor. He wants to know if God might give him the gift of a guitar if he sacrifices his money to the church. As a symbol, this shows his willingness to entertain a moral or ethical perspective of reality, but more importantly, he must ask once he got his guitar whether it was related to the sacrifice or not.
The dog
The dog allows the boy to earn his $20 by being lost. He is able to find the dog's home, and when he gets there, he elaborates a story. The story and the dog itself are a portrait of the artist and the muse. He takes true emotions and elaborates them in prose, and earns a little money doing it sometimes, just like the boy's serendipitous reward.
The television dream
When Fausto sees Los Lobos in the opening scenes, playing their guitars on television, he realizes what he wants. He wants to be able to celebrate his own point of view for his own screaming fans. The request is for glory and for self-mastery, because not only does he want the guitar, he wants to be on television. The TV is a symbol for fame and glory.
The surprise guitar
The symbolic surprise is a a reminder of the serendipitous nature of good luck—or God's blessing? The boy must decide for himself. The guitar symbolizes a new journey, and his experience of getting the guitar was a strangely passive one. The guitar represents hope, because he is surprised by getting what he wants in a way he believed was impossible.
The parents
Though the parents aren't sure they can afford to by Fausto a guitar, they end up finding one to give him anyway. This is a symbol for the profound resource of a loving family. Because he is loved, little lucky moments like this happen to him. If he was alone, like he often wants to be, he would have been limited to his own resources. The parents symbolize his willingness to ask for help and to be in community.
