Lindsey Vonn -- Bikini Workout ... During Mexico Girls Trip

No days off when you're a pro athlete ... even during a beach vacation in Mexico ... just ask Lindsey Vonn who workin' on her fitness while workin' on her tan.

Vonn and a bunch of her besties just got back from a girls trip to Cabo San Lucas -- but you can see in the pics, it wasn't just about margaritas and tequila shots ... Vonn was determined to keep her ass in shape.

Even with a busted ankle, Vonn knocked out some side bends and planks ... with her friends even giving her a spot.