If you’re at a restaurant in Mexico, what is the word for “brains” that would appear on the menu?
According to babelfish, it’d probably be “cerebro de la vaaaaaaaca”.
The most likely “brainy” thing you’d see on a menu is tacos de sesos. Recipe at the bottom of this page (in Spanish).
(More generally, sesos means brains in the culinary sense.)
Another term I see at the local taquerias is “cabeza” or head. I don’t know exactly what that’s referring to, but I’m assuming they’re not serving up skulls. A burrito around here is roughly the size of a 16-oz can of beer, so a skull wouldn’t fit. 
Ahhh… some Googling turns up that cabeza is beef cheeks. I never bothered to look before now, as this gringo gets enough quizzical looks when he asks for carne desebrada. (similar to well-cooked, falling apart pot roast in a spicy chili sauce)
As a side note, if you’re at a restaurant or taqueria and see things like sesos, cabeza, lengua (beef tongue) and birria (goat) on the menu, you’re probably in a decent place. One that can’t be bothered to have anything beyond beef, chicken and cheese probably isn’t much more advanced than Taco Bell.
Interestingly, it’s related to our word “sense”.
We have Sp. peso from latin pensum (“weight”)
so it makes sense that we also have
Spl seso from L. sensum (??). I’m not sure of the exact Latin form, but I’d bet my next paycheck that it’s pretty close to that.
Brain is *cerebro * in Spanish. However, when talking about animal brains and not referring to anatomy we usually use sesos. Cow brain is sesos de vaca, no sesos de la vaca, as the latter implies that you refer to the brain of a particular cow. Although quite rare we eat goat brain around here, we also eat tripes (just as the Spaniards) and other less than elegant body parts.
I’ve tried them.
I gather from context that it is “anglos”.
cow: female
cattle: male or female
Just a guess… is the OP playing the “Where are you?” contest in Conde Nast’s Traveller magazine?
Or sesos de res, “res” being an alternate word for referring generically to bovine meat.
Yum. Mondongo.
Another personal favorite of mine: Gandinga. It’s a stew of, in my brother’s definition, all what’s inside the pig that you don’t use for sausage.
Just sesos would probably be the most likely form. Beef brain being the most commonly consumed.
Tacos de cabeza can be from any part of the head. That includes the brain (de sesos), the lips (de labio), the eyes (de ojo), the tongue (de lengua), the ears (de oreja), the cheeks (de cachete), other meat scraped from different areas (de carnaza) and a few others. You order whichever pleases you.
The taco de cabeza stands are easily recognizable. The different cuts of meat are placed in a type of steam tray and covered with a large white towel. Some carts or stands are adorned with a bleached cow skull complete with horns.The tortillas are heated using steam. Usually they are served with chopped fresh white onion and cilantro and a salsa verde. Tongue is probably the most popular filling and usually gets sold out before the others. In fact the demand is so high for beef tongue that Mexico imports large amounts from the USA.
And with good reason. When I was young, I went to visit some of my cousins (on the Mexican side of my family). My aunt was cooking some meat in a pan, which she proceeded to slice up and serve as sandwiches. It was delicious, incredibly tender, and I finally asked her what it was. When she said it was tongue, I stopped chewing briefly, but then decided it was too good to stop. In all seriousness, I don’t ever remember having a more tender cut of meat.