The two youthful gypsies who thrilled theatre crowds by staging a revolver fight with more than a score of patrolmen throughout the white light district both pleaded guilty when arraigned in court. Joe Peterson, 25, whose band is in camp at 50th St. and Maspeth Ave., Queens, pleaded guilty to a charge of disorderly conduct when arraigned before Magistrate Thomas F. McAndrews in Yorkville court and was fined $5. His companion Steve Mort, 25, arraigned on a charge of driving while intoxicated, was remanded for investigation and sentenced Friday when he pleaded guilty before Magistrate Ewald in traffic court.