I believe it has to do with the 'Hispanic culture' here in the US. It's more like the black culture than the Mexican or Central American culture. They've adopted the ghetto mentality, and in many cases are just not interested in education, and actively ridicule those who are. This attitude breeds hopelessness and a feeling of living for today, which will always increase sexual activity because they believe there's little else to live for.
I understand what you're saying, but then how does that explain Girls Gone Wild? You can either have sex because you have nothing else or you can have sex because you have everything.
Ghetto mentality... that's rich, I'll make sure that Hispanics like me and my girlfriend buy our third house on the beach in the local ghetto. Ignorant-flat out.