The Weeknd Party next door
The park near the Iglesia Ermita is El Bulevar.
Keep in mind this is different from the recently opened Bulevar del Oriente.
They have weekend Rumbas (street parties) there every non rainy weekend a great place to meet people and people watch.
The Park is interesting in itself for the culture vultures out there.
It's possible to dance with an meet a non Pro there though I must admit I know of very few expats or visitors who pulled a girl there as they usually come in groups with dudes.
Hope this Helps.
Trip.