Oh, Tango isn't that popular in Argentina, not too many people know how to dance it or even listen to it regularly. I guess I would compare it to the jazz scene in the US , but I'm not American so I wouldn't really know.
On the other hand, even though it isn't even half as popular as rock music, it does permeate argentinian culture. Gardel is like Elvis and I'd bet most people know at least a couple of tango songs just by cultural osmosis and the tango lexicon is synonymous with Rio de la Plata spanish. And the "World tango dance tournament" is reported on mainstream Argentinian media every year.