329 E Main St
Monroe, WA 98272
Pihuamo is a small town of 8,000 people in Mexico, and, while Monroe is clearly much larger, it does seem fitting for a taco truck named after a small town to be in a small town.
Tacos Pihuamo is everything a taco truck should be: it has great food, more types of meat than menu items, a one page tick-mark accounting system, and it's located directly adjacent to a train track. It's also just off Highway 2, which makes it a great place to stop when you're returning to Seattle from a hike in the mountains.
While the menu is simple, the dishes are great. Get a variety of meats on the tacos (or stick to the always really good carnitas) or get the quesadilla, which could be named the taco-mondo because it really is just a mammoth taco. Vegetarians get the goods here - they throw tasty beans on your taco in place of meat.
Things to avoid at Tacos Pihuamo: the horchata. It's too sweet and too thin. Stick to the Jumex or the Jaritos.
Things not to avoid at Tacos Pihuamo: the candy. Mexico is now regulating, with some efficacy, the amount of lead in children's candy. Try it.
Just because the truck isn't there when you go by in the morning doesn't mean that it's gone - they actually do pick up shop and leave every night (or at least some nights). They'll be back around 11 or 12 and a picnic table will be waiting for you.