We did a similar taco survival guide for SXSW but this is more thorough. Read this, understand it, and use it.
Jay from Guns & Tacos says:
To optimize your taco-eating experience, I thought I’d relay a few tips that might prove helpful. Some are pretty basic, so bear with me.Taco Stand Translation Guide
1. Always bring cash. Preferably small bills.
2. If you’re not a fluent Spanish speaker, try English first. Most taco truck attendants have remarkable psychic abilities and can interpret your hungry non-Mexican gestures and awkward, ugly English quite well. Also, if you start using Spanish, they might think think you are fluent and respond in really fast Spanish.
3. Do not allow them to put lettuce and/or tomatoes on your taco. If this happens, write “CILANTRO Y CEBOLLAS” across the side of the taco truck with the nearby red salsa squirt bottle.