Steve and Cody took me to a bar in Playa tonight, called "Señor Frog's". For 300 pesos (USD$30), they'll give you anything they've got, totally unlimited, for 3 hours. Considering that a single Margarita (a massive one — app. 700ml) is 190 pesos, this is an awesome deal. But it turns out that getting through more than a few of these jumbo frozen cocktails is quite a challenge.
I managed to guzzle about 4 cocktails, including Margaritas, Piña Colatas, and "Señor Frog's Special". There were, of course, various assorted shots and beers in amongst this. After that, my stomach positively refused entry to all additional liquids. The quota was filled. The next cocktail on the bench had about as much chance of getting in as an Iraqi family in Villawood.
But I got off lucky. Cody exceeded his quota by a bit, and all his cocktails wound up getting deported, pronto, out his mouth. Wasn't much fun for him. And didn't really impress the 2 German girls in the bar with him, either.
If it's large, tasty, highly alcoholic, good value beverages you crave, Señor Frog's is the place to go. But just remember that when your stomach says "enough", it means it.