As a title, The Circuit references all of the moving around the characters do in this book. After all, a circuit is basically a journey that goes around and around—and then around some more. And if there's one thing that Francisco and his family know how to do, it's move among the same few cities in California, right along with the seasons. Francisco finds all this moving to be seriously exhausting sometimes, but the circuit they travel is also what keeps this family working and building their lives in sunny Cali.
Because of this—because they're location rotation is something the family does to build their life together—perhaps the title references another, more subtle circuit: the connection between Francisco and his family. They're regular moves make friendships hard to form, but at the same time it also keeps them a tightknit unit—which is a circuit in its own right.