I know of no night classes. But a more likely scenario is a language exchange. Find a Korean friend who wants to study English and is willing to trade for Korean lessons. The Skype English Club (check out ulsanonline.com/Culture for a link near the top) would be a great place to find a Korean who wants to study English if you don't already know one. In my experience, though, you can throw a stick down any street and hit a dozen people who would want to study English.
Martin

