Eh, don't listen to Rotten Tomatoes. It's like a bunch of wine connoisseurs disliking a drink and comparing it to wine, but in actuality, they got a mouthful of 4 Loco. Judge it for what it is, and what it is trying to do.
This movie, simply put, is an insanely fun, grotesque and darkly humorous action flick. I'd put it into the same category as the Crank films. Would recommend.