There is a different theme every night- tonight I believe it's 'Inditas', when everyone dresses up like Aztecs. It can be a surprise to see local shop owners and young people in full costume, doing an 'Indian' dance much like we see in Canada at a potlatch.
The last night - or 12th night - is the night of the Virgen, which is tomorrow. There will be a 'Castillo' or fireworks tower in front of the Church. Not sure when the fireworks start, I will try to check.