The celebration is called Lupita's Day and it's based on the worshiping shown to the Virgin of Guadalupe. This is a celebration where whole families gather to go to church and also to walk on the "malecon" and streets all day long getting ready for the night. You will also be able to see processions of people carrying images of her as well as ceramic figures; many main streets are closed to allow the free passing of people, and after a while, all people gather at the Cathedral of Guadalupe (one of the most representative landmarks of Puerto Vallarta) located right in downtown where a special mass is held. If you're into tradition and religion, you don't want to miss this out.