It can be easily a street, parking lot, a park or the entrance of another building, some people in Latin America are too poor to afford a big room with tiles for this sort of events that they must lend the dress for a while and the rest is a debt, if there's a girl born in a poor Latin American country, then, the parents aren't just worried of affording food, education, clothes but the quinceañera stuff when she'll be 15 y/o, it doesn't matter if they are poor enough, they try to do something nice for her, for the alcohol or for the sake of traditions which almost nobody knows what is for.

So, it seems like they couldn't afford a tiled place for dancing but they wanted to do the celebration.