I'm not a newbie.  But I don't know the meaning of this lingo, "mexican".  Its usage was as referring to a particular sexual activity,like "russian","french",or "greek".  Any help?

Buritto up her ass, and then eat her salsa. LOL    Seriously, I've never of Mexican and I'm no newbie either.

I believe Mexican involves taking the penis directly from anal to oral.

Oh, ATM!

I have no idea.
However while I was in the porta-john yesterday I did see a posting on the wall:
Neded two Mexicans for Mud Flaps.
Must be flexible and willing to travel!