Hi Pearl
In most of the milongas (places where locals go to dance tango) there is a show
You have to google the places at el tangauta
I can mention you just some of them where you can also take tango dancing lessons for the same price of the milonga
that is 30 approx, pesos in all, it includes the lesson and the possibility to go and see tangueros dancing.
I can recommend you Grisel, Porteño y bailarín, Salon Canning, Niño Bien,
or La Ideal on suipacha and Corrientes.
to have dinner I would advice you to go to a restaurant before, unless it is ok for you to eat some empanadas very basic menu.
In addition 2 americans are running their own milonga :
one is on Recoleta: La coqueta de Recoleta on mondays
and anotherone in San Telmo : Flor de Milonga on tuesdays
Enjoy your Tango tour
Maria Teresa