If you are in Argentina at this time, it would be almost a tragedy to miss this! Many events are organized in the city, mostly concentrated around the San Telmo Tango region. The price of registration is a bit steep, but if you’re willing to splurge for some exciting nights of dancing, this is the festival for you. The website has information in English.
Web Site: http://www.mundialdeTango.gob.ar/home09/web/en/index.html