The Rocks is a busy area, with late trading, and a comfortable feeling. Late at night, the concentration of pubs can inevitably lead to some alcohol fuelled violence. The area is well patrolled by police, but some fights do occur in the pubs and on the streets. Use common sense when interacting with drunk people, and you will just be a spectator.
The Rocks police station is on the corner of Argle and George, just opposite the Argyle Hotel. It is one of the major central Sydney police stations, and is easily accessible at all hours of the day.