What makes you sick in Mexico?

For the concerned reader in Massachussetts who wants to know what to expect to get sick from in Mexico, the short answer is: everything... and nothing.

Everything: (If you choose to be paranoid):

• Tap water (except in hotels that claim it is safe to drink).
I do brush my teeth with tap water in Mexico. And I don't tape my mouth shut as I'm taking a shower. Just so you know.
• Strawberries
• Watercress, lettuce or anything leafy green
• Evidently now, some local jalapeños. Go figure which.
• Eating unwashed fruits with the peel on.
• Oysters and other molusks (in the months without an "r", from May to August)
• Raw fish as in sushi.
Evil lurks everywhere.

However, if you will pardon the pun, it is a crapshoot. The fact is, you may eat watercress salad with cilantro and jalapeño and apples and nothing will happen to you. You may eat at a fancy restaurant and get the runs; you may eat at a taco stand and be spared, or viceversa. The fruits and veggies listed above, although probably safe in clean places, (and many fancy restaurants have imported lettuces) have a higher possibility of being in contact with polluted irrigation waters, which is why some people think they are not advisable.
I don't eat oysters in Mexico City. Period.

Nothing:

• THE ICE WON'T MAKE YOU SICK. If it is in cubes and you haven't seen it being dragged through the streets as a dripping block the size of a safe, YOU CAN DRINK; HELL, YOU CAN EVEN CHEW THE ICE. The reason why this is in caps is because I am tired of answering this question.
There is plenty of bottled water everywhere. Over there they haven't heard about the environment yet. You can litter the Earth with the spent plastic bottles of water you drank in Mexico.
• There are several perfectly logical reasons why people get Moctezuma's Revenge, which if it makes you feel better, doesn't really discriminate. It attacks the locals as well.
1. Your intestinal flora may not be used to the local bacteria. I used to get sick every time I came to the States. That, I guess, was The Alamo's Revenge.
2. Mexican food is elaborate and uses lots of spices and ingredients, that may feel a little heavy. It's very easy to overdo it as it is SO GOOOOOOOD.
3. Easy on the Margaritas, pardner.

Now. Going to Mexico and worrying about the Revenge will probably make you sick. I have known people with otherwise delicate constitutions that have never ever gotten sick from food in Mexico and my theory is that it's because they surrender to it with gusto. I recommend you do the same. (Disclaimer: I will not be held responsible for your runs or any such events in case they happen. Bring the pepto and the immodium if you need a crutch, although you can find both in abundant supply at any pharmacy).
Do not be like someone I knew who would travel frequently to Mexico on business and all she ever had for lunch and dinner was grilled chicken. This is a crime.
The fruit is magnificent, the food is sublime.
If you see a guacamole, have it; I command you. You will see the light.

Enjoy!