Most Taekwondo Gyms (in this area) cost around 80,000~100,000 won per month w/ training Monday through Friday. There are several gyms in Seoul that give instructions in english and to adults.
Arirang Taekwondo // 아리랑 태권도장
http://www.facebook.com/groups/79149497926/I have been to many times when I visit Seoul.
Hanwoori Taekwondo(Seoul)
http://www.facebook.com/hanwooritaekwondo"If anyone is interested I have a friend in Shinchon that owns a school specifically targeted for international citizens."
There are some others depending on where you are. ^^
As an Assistant Teacher at a Taekwondo Gym, we go to tournaments quite often depending on what the students (children or adults) want to do.
Some of the tournaments are small and local while others encompass a larger area and numbers of people.