When I first arrived in the city I went to a place called LA VIRUTA (tango?). Can't remember the address but it's on the internet if you do a search. Not close to downtown but I'd recommend it as they have Salsa lessons downstairs in a community center and there were about 300 people there. Different areas of the room for the different levels of dancer. Costs 6 pesos to get in and the lessons last until about 1 am and then everyone just dances the night away. Went until the wee hours of the morning and this was on a thursday.
Hi, my name is Constanza, I am a Colombian girl who teaches salsa on my free times of shcool, I teach with a Colombian style of salsa dance with a very good and fun and personal method, I go to the place you live. If you are interested, just write me at this mail firstname.lastname@example.org