Performed masculinity (Situational Irony)
Julio and Tenoch present themselves as the epitome of masculinity, playfully fighting with one another, calling each other "faggot," and engaging one another competitively on the subject of sex. As the film progresses, however, they reveal themselves to be sexually inexperienced and naive, each with no idea how to pleasure Luisa sexually. Then, on the final night of the trip, their perception of their own masculinity is undermined by their romantic interest in one another and their erotic connection. Thus, we can see their performance of masculinity as ironic in that it masks a deep insecurity and a latent desire for one another.
Jano's affair (Dramatic Irony)
Luisa initially has no interest in going on a trip with Tenoch and Julio, but when she discovers that her husband Jano has had an affair, she decides to take them up on their offer and go on the trip. While we know about Jano's betrayal, and thus the reasons for Luisa agreeing to the trip, Tenoch and Julio have no idea, so there is dramatic irony due to the fact that we know something the teenage boys do not.
Heaven's Mouth is made up (Dramatic Irony)
While Luisa is keeping some secrets from her traveling companions, they are also keeping a secret from her—the rather pivotal secret that the beach they promised to take her to, "Heaven's Mouth," isn't a real place, but a fabrication meant to impress her. As they drive towards a number of beaches, Luisa believes that the boys have a specific beach in mind, and does not know that they are improvising.
Heaven's Mouth exists (Situational Irony)
After believing that they have totally pulled Luisa's leg about the beach called "Heaven's Mouth," Tenoch and Julio are startled and delighted when Chuy, their tour guide, points out that a nearby beach is actually called "Heaven's Mouth." In an ironic, almost magical twist of fate, the fictional beach that the boys created turns out to be an actual location. Not only is it real, but they also happened to bring Luisa there without even meaning to.
