uI lived in San Telmo for 5 weeks back in the winter of 2007 and I wasn't going to come back after I flew out in late spring. But fortunately I moved to Recoleta in early September and my final ~10-11 weeks were spent in a neighborhood that wasn't a dirty ####hole.
There are times that I go to San Telmo and think- "Wow, this isn't the worst place in the city to live." Of course my old roommate was mugged with two other girls at knife point in San Telmo, but it was their fault. They were talking to each other while waiting for a bus. They might as have been flashing their boobs. I mean, if you are waiting for a bus late at night, you're just asking for someone to rob you.
As long as you aren't living more than 3 or 4 blocks from Plaza Dorrego, you probably won't get mugged in front of your place. I never did and after living in a 3rd World hostel on Dorrego near Independencia, I moved to the first blog south of the highway where I had to pass a large group of homeless people sleeping under the bridge every night. It was AWESOME!!
San Telmo has some lovely buildings. I was walking through there 2 weeks ago snapping away at images with my camera. I give tours, so I have to go there and (even worse) La Boca several times a week, but that being said, I was walking through San Telmo during the day 2 to 3 weeks ago and was amazed at the buildings on Chacabuco & Piedras. There really are some sweet buildings. But it's proximity to Constitución & La Boca just makes it such an unsafe place.
Most probably, nothing will happen to you. But when you're in your lovely old building, just ignore the trash on the streets, the dog poop on the sidewalks, the annoying kids hanging out in the squatters' building on your block, and the lack of legitimate police presence.
