Ok, I'm biased because this is the area of Buenos Aires I've chosen to live in, but here's why. I love the authenticity of San Telmo. It's gritty and a bit beat up, but it's also lively, funky and welcoming. The massive street fair on Sundays brings in hordes of people. On the other days of the week, San Telmo changes greatly depending on what time of day you're here. There are lots of new cafes, restaurants, boutiques and the like, but it's still not the trendiest neighborhood around so there's less snobbery. I love the architecture, the graffiti, the indoor market, the street vendors at Plaza Dorrego, the outdoor milonga on Sundays, and the fact that I hear way more Spanish than English everywhere I go.