I did something foolish on my trip to Mexico City. Well, actually, I did several foolish things, it being a major birthday celebration/avoidance trip, but I'm only going to tell you about one of them. And for the record, I was not thrown out of that bar; I was ready to leave anyway.
Mexico City is full of street vendors selling all manner of foods. Many of them set up ramshackle tents and tables with crude seats for people to sit at. It all just looks like such a wonderful experience, and the food looked and smelled so tempting each time I passed one.
But those not assimilated to bacteria found in Mexico may eat at one of these street vendors only at their own peril. Even in established restaurants where it's safe to eat it's best to avoid foods not fully cooked — salads, for example — and even drinks with ice cubes. Montezuma, it turns out, was a very vengeful dude.
But there's another type of eatery that seems to fall between established restaurant and pop-up street vendor. They're technically brick and mortar businesses — they're under a roof, but they're typically wide open to the street. Their sanitation practices are a bit hinky.