What is the average recovery time of an AC joint surgery?

Depends... Depending upon the severity of the injury, the skill of the sugeon, and the overall health of your body in general i would say 6-12 weeks.
Recovery time varies. Recover time will vary depending on many factors including age, general health of the patient, infection control, smoker or not, blood sugar control, the exact type of procedure, and post-operative and follow up care. Discuss it with your surgeon and get their opinion as to what they feel is a reasonable recovery time for you.