Antonio knows about Rosie's and the prostitutes that work there. He hears talk about it, and he believes that the women and men there are committing acts of sin. When he sees Andrew there, it upsets Antonio greatly. Other than that and the occasional debate about the Virgin Birth, there's not much talk of sex in the novel, and there's also virtually no romance to speak of. Although, the Vitamin Kid does give up racing across the bridge so he can walk slowly across it with a girl he clearly likes.