It is true that Avianca MDE-BOG is like a bus service - they have something like 15 flights a day each way. That said, I would not cut it too close. I fly that route a lot, and often by the end of the day those flights are running 1 to 2 hours behind schedule. A little fog delay in the morning in BOG screws up the intra-Colombia schedule for the rest of the day.

If I was in your situation, I would book my MDE-BOG flight to arrive no less than 2.5 hours before your flight out of BOG, particularly if you have checked luggage.