Through the miracle of Ravelry, I "met" Marcela, who lives in Buenos Aires. She recommended a yarn shop called Milana Hilados and "introduced" me to Joji, who works there. Fun, fun, fun!
I looked at a number of other yarn stores on Scalabrini Ortiz, but Milana was by far the best. The others had too much acrylic and bulk commercial yarn, while the yarn at Milana is high quality and creative.
All of that yarn shopping was so exhausting, we needed coffee to restore ourselves.