Some Slang Used In Mexico
I don't know it all, but here are some of the slang words and uses I have picked up in Mexico. Some of them may actually used in other Latin American countries as well.

Güey- Probably the most used slang in Mexico. It is like "dude," and is used ALL the time (pronounced almost like “way”).
Pinche- fucking (adj.)
No manches- No way! Not to be used in formal situations.
No mames- No way! The cussword version. Definitely do not use this in formal situations. literally it basically means don't blow me.
Mamada- blow job
@- used when a word can be male or female, to represent both the “O” and the “A” in the word.

The Vines of Mendoza is a truly amazing gathering place for wine lovers. It's hard to describe the business because it is many things.

Tasting Room, Wine Bar, Education Center in Mendoza, Argentina

Relatively common in Spanish slang (and particularly the Spanish of the southern cone South America) is the set of words requete and the prefix re-. These all serve to emphasize the next word in the sentence.

So, "re-caliente" would mean really hot, like it is in Mendoza right now. You could also say that "el tiempo es re-feo" or "requete-feo" meaning really ugly weather.

Re is also a homograph for "rey" or king - hence my feeling that this is the "king" of superlatives. I'm hilarious, I know.

I recently learned about the resource Single-Serving.com which provides single servings of language learning. In our trip we have 3 days/2 nights in Paris and are more than a little concerned about not knowing any French. Our Spanish is solid, and our Dutch is passable, but French is a weak point. Hopefully they'll take pity on us, but learning a few phrases from the French resource page will really help.