Canelo Alvarez and Caleb Plant couldn't wait 'til November to try to punch each other in the face ... 'cause the two just exchanged blows at a pre-fight event, with Alvarez making Plant bleed.
The boxers stared each other down before taking questions from media members in Los Angeles ... when suddenly, things got intense between the two.
Broadcast cameras showed Canelo shoved Plant ... and then repeatedly called him a "motherf**er."
That's when Plant came back and tried to land a huge haymaker ... which Canelo appeared to dodge.
Canelo then tagged Plant with a flurry of punches -- knocking off his sunglasses and causing the fighter to bleed from his right eye area.