In The House of the Scorpion, everyone but Matt seems to be in on a secret. Even when that secret is revealed to Matt, he's still in the dark about a lot of other things, and he remains in the dark only because of the atmosphere of lying and deceit that El Patrón has created in Opium. There are all kinds of lies in Opium – ones that are total secrets (like Tom's parentage) and others that are open secrets (like Matt's being a clone). These secrets are kept secret because they are threats to El Patrón's power, and also because they are painful to acknowledge. Growing up in such an environment means that facing the truth is a hard lesson for Matt to learn. But he definitely learns it, with the help of Esperanza's shockingly truthful book, A History of Opium. Our hunch is that when Matt returns to set things right in his home country, he'll need to expose all the secrets that allowed El Patrón to have total control for so long.
Matt deliberately blinds himself from certain truths about El Patrón, Opium, and his own nature because they are too difficult to handle.
Matt doesn't learn the value of the truth until he is on his own and fighting for survival in Aztlán.