Avianca Business Class is good. The food is served in a professional manner. Of all the latin airlines, I would rank Avianca 767 Business Class service among the best. You will enjoy the comfort - however, keep in mind that the 767 product is dated.
As far as Bogota is concerned, the city is fine. You can check all your hand luggage at baggage services (to the left as you exit the terminal). The fee is reasonable and they give you the key. The taxi ride downtown is simple, the cabs have meters and the people are in my opinion among the friendliest in Latin America. Try out some great pizza by the cathedral plaza downtown. Keep all your valuables locked up at the airport and you should have a nice time.
The downtown area is about 25 minutes from the airport. Remember to have your passport stamped "Transito" BEFORE you proceed through customs. There is a transit counter after immigration to your left. No charge for the stamp. You must show onward tickets. If you do this this, you will avoid paying departure taxes.
Enjoy your trip.
Dave