This was a great little find! Very cheap, and in a handy location (the street itself isn't great, but it's a quick walk to the centre of San Telmo, and to the Microcentre). The building's lovely with lots of character and some charming details. The room we had was small, but nicely done and again managed to retain character. The free internet was a bonus, and the roof terrace was great!
My main complaint was that there was no air conditioning in our room, and there was only a ceiling fan, which helped, but not enough in the heat of summer.

The best thing about this hotel is the staff - they are a friendly bunch and try to make your stay pleasant.

Overall the hotel is clean and tidy, with a character. Of course, if you want 4-5 stars, do not bother, but if you want a decent place to crash with wi-fi Internet and a practical breakfast, Don Telmo is a good candidate.

The location is good - close to the historical center, Microcenter, La Boca, Puerto Madero etc. The street (Mexiko) itself is quite dirty and casual but safe and OK. Again, if you fancy chic, there is Avenida Alvaer in Recoleta :)

I stayed 2 times over a period of one week there, they also allowed me to leave my suitcase at the hotel for 3 days so I could travel to Iguazu light.