Post in the Avianca forum for more experience would be a thought. Lifemiles.
They and Copa are ruthless with on time performance so I'd count less on them vs. other airlines with being loose on the rules.
That said, when I used to fly Avianca (when it was TACA), J check-in took all of 5 minutes (even without e-check-in which I do not trust with these airlines because of their hopeless IT and web sites) due to the low number of flights (e.g. one) and the small cabin. The rest is the airport and airport service companies.
I would worry more about security and other queues than Avianca. That said I would not risk 90 minutes.