Patrick and Brittany Mahomes might be on vacation, but the trolls seem to find them regardless ... with some hardcore Raiders fans giving them guff as they left a restaurant.

TMZ obtained video of the pair grabbing a bite at Rosa Negra -- a luxury Latin restaurant in Cabo San Lucas, Mexico -- Thursday night, and it looked like one hot date night for the couple, sans any kids.

Eyewitnesses say the couple hung out for about two hours before dipping out ... and, that's when they got heckled by some fans of an opposing team ... with some goons booing and hissing them, not to mention shouting "RAIDERS" to Patty and Brit as they bounced.

It's all clearly in good fun here -- though pretty bold of LV fans to troll Mahomes to his face. But, we doubt he's sweating it ... remember, Pat won a Super Bowl on Raiders' home turf about two months ago -- so, ya gotta think he's got a leg up on Las Vegas these days.

BTW ... even though the couple's enjoying their vacation, it doesn't mean they've totally forgotten their friends. Brittany posted a message in support of her new bestie Taylor Swift after she dropped her 'Tortured Poets' album.

Clearly, she isn't letting the world forget they're besties now ... even from south of the border.

Anyhoo, Patrick and Brittany are having a grand time ... one that's apparently never-ending. They've been vacationing for a helluva long time now -- this is actually their second time in Mexico in about a month. Since winning the Super Bowl, they've been jet-setting a lot.