11:54 AM PT -- The Menlo Park PD tells TMZ Sports ... cops detained two people involved in the incident -- and determined they were both intoxicated.
Cops say they tried to speak with key witnesses, including McDonald and Lloyd -- but they bounced before police arrived.
But get this, a hotel security guard told police he tried to stop the men from leaving ... but claims "he was purposely pushed out of the way."
The security guard later told police he did not want to pursue any action against the guy who pushed him.
As for the fight itself, cops say everyone involved has decided NOT to press charges.
9ers stars Ray McDonald and Brandon Lloyd jumped into action at a San Francisco-area hotel -- breaking up a FIGHT between a drunk guy and two women ... TMZ Sports has learned.
Law enforcement sources tell us ... McDonald and Lloyd were at the Rosewood Hotel in Menlo Park around 2AM Friday when a man who appeared to be super drunk began shouting at the two women who had been hanging at the bar with the players.
Witnesses tell us ... the drunk man called the women "whores" ... which obviously didn't go over well. We're told things quickly escalated with the women eventually charging at the man in a violent manner.
That's when the NFL stars rushed in and broke things up ... and then left the hotel when they felt the women were safe.
Cops were called to the scene -- and they took a report on the incident after talking to witnesses at the hotel ... but we're told no charges have been filed against anyone.