The reason that the teenagers listen only to reggae music is that this film was actually shot in Jamaica.
The "Dreamland Theatre" shown in the film is actually The Ward Theatre in Kingston, Jamaica.
The title "Popcorn" was linked to an element in the story. This element was removed before the final cut. The producers and distributor liked the title so it was kept.
This was such a box office disappointment in the United States that in many markets it bypassed first run cinemas and was booked directly into second run/discount cinemas.