I walked by this cafe at least a half-dozen times before discovering it. It's location across from the BP isn't great, but inside the cafe is very nice. There are several tables set up for socializing. The atmosphere is very calming inside. The pastries are tasty and homemade, though served on styrofoam plates. Tango Cafe also has mate, a herbal tea consumed in Argentina and Paraguay.
The service isn't entirely enthusiastic, though pleasant. Spanish lessons are held at the cafe in the evenings.