I just returned from Buenos Aires as well and did 3 "blu rate" transactions. When I checked into my hotel I asked the clerk and he offered me a rate of $8. Since I was tired and jet lagged I just exchanged $50 to get me started. The next day a tour guide took me down to Florida Street and we found someone who gave me $9.6 A couple of days later I was passing by a restaurant in Recoletta and they had a small sign offering $9.5, so I had dinner there and did another exchange.