Marshall you will probably come across
Palacio Gaviria in your search for discotecas -- it is located on Calle Arenal and has several different rooms, at least one of which plays techno music. Kapital, a disco with about 10 stories, also plays techno music but I can't remember where it is located.
Enjoy!
[This message has been edited by MadridMan (edited 01-09-2001).]