In Korea, there are many regional festivals. I recommend going to Hoengseong Korean beef festival held in Hoengseong, Gangwon province. Hoengseong Korean beef is renown for its delicious taste. At the festival you can buy Korean beef at a good price.
At Jinji, Gyeonsangnam-do, Jinju Namgang Yudeung Festival is a great festival. At the festival you can see traditional lanterns on the beautiful Namgang river. Moreover, 1200 scenery and customs of 31 countries.
In Yeonggwang, Jeollanam-do, 2012 Forumla 1 Korean Grand Prix will be held, where you can watch F1 cars race. Korea, at the moment, is full of things to see and taste. In Korea, you can surely enjoy autumn.