Bike nights are at Wing House over by Tinsel town on Trursday nights. Sneakers on Baymeadows has a combination sportbike and cruiser bike night on Thursday also. They have group rides here all the time on weekends if you show up and meet a few of the people. They mostly hang on another forum but I won't post the link as I don't the rules around that.
They also do a Georgia ride every weekend that some from Jax go up and join, but from what I understand, you better pack a chute if you go on that ride.