Often, the Broadway musical crowds can seem to be totally enveloped by two basic groups: The theater gays, and the theater tourists. Which is just fine. But when an average chump (hello!) not blessed with either the Broadway savvy of the first group or the utter lack of self-consciousness of the second has an occasion to wander into the theater, it's hard to know what to see. So we are here to give all the middlebrow people among you this valuable advice: It's all about "In the Heights."