Sean and I chose to do the CELTA course in Colombia because we wanted to experience a place other than Brazil for 6 weeks. In Colombia, we had the choice of doing the course in Medellín or Bogotá and we went with Medellín after hearing really positive things about it from both friends who had visited and Colombians who we met in Brazil.
Citizens would go out of their way to help us and were always incredibly friendly. More than once we were verbally "welcomed" to the city just because people noticed that we were not from there. The hidden gem of Medellín is starting to catch on, however, and we met quite a few expats from Canada, Europe and the U.S. who had decided to make it their permanent home. All of the other CELTA graduates were intending to stick around and find work in the city - Sean and I were the only ones who were planning on leaving.
Another impressive thing about the city is the transportation system. Medellín has a metro (Bogotá doesn't) and the metro system includes buses as well as cable cars that go to neighboring mountain towns. This allows people from quite far distances to get into the city center quickly, efficiently and cheaply. The cable cars offer impressive views of the city and the day we rode one all of us in the car were tourists and were just along for the panoramic shots.
The most common things to eat here are arepas, which are thick corn tortillas covered in fresh cheese. Sean's favorite dish is the huge bandeja paisa which includes a fried plantain, avocado, sausage, rice, beans, arepa, egg, bacon, ground beef and coleslaw. The national drink is a liquor called Aguardiente made from sugar cane that is flavored with anise.
We didn't have a lot of time to do much sight-seeing but spent one full day down town checking out some churches and squares and visiting several sculptures of Botero. We spent another day visiting the botanical gardens which were abuzz with yoga classes, dance demonstrations, food vendors and a marching band festival. We're glad we were able to stay such a long time in such a pleasant and enjoyable city. Medellín - highly recommend!