I also went to a bull fight in PV. The beer guy came over and I asked for 2 beer. 40 pesos he said. I gave him 200 pesos and waited for my change. He then put the 200 pesos in his pouch and asked the person next to me if he wanted a beer. I said to the beer guy "where is my change?" He then started getting mad at me and pointing to the police and saying he was going to get the police after me for hassling him. Then he had the nerve to ask me to pay the 40 pesos for my beer. I didn't want any trouble so I reached into my pocket and gave him 40 pesos in exact change.
Moral of the story... never use a large bill when paying for small ticket items... that is when you will get ripped off. If they ask for 40 pesos... give them 40 pesos.

If you ever go to Puerto Vallarta and go to the bull fights, do not order beer for the old guy who pours beer with one arm behind his head. That is his trademark pour... that is the guy that ripped me off if plain sight and in full daylight.