I used to live in Colombia (Bogota) and found Avianca to be great at one point in history. They've gone way downhill in the past 8 years or so. Too bad

Continental is great, especially if you want to avoid flying through Miami. COPA is ok if you don't mind a stop in Panama City :0 I found in my many flights in and out of Colombia that the best route was via Newark or Houston or pretty much anywhere other than MIA. The flights in and out of that city --especially on Avianca and American-- invariably got delayed and the service was bad, flight crew cranky. Once I started going Continental and using Houston to go to Colombia, Ecuador, and Peru, I've never had another missed connection, late flight, or unpleasant experience.
Hope you have fun in Bogota

If it is a busy travel day, allow 1 hour to get through the DAS (emigraciones) line so that you don't miss your flight back to the US, and no, Avianca (unlike the rest of the airlines) will not come around looking for you in the emigraciones line or page you to make sure you get on their flight. Their attitude is: if you miss your flight due to the long line, it's not their problem! That's service!