Decided to start an "official" taqueria (and more) survey. I was tempted to start with Portland proper, but the offerings just aren't as exciting as those in Hillsboro so that's where I began. I went to the three most prominent taquerias/restaurants: Ochoa, Maya's (in Su Casa), and Flor de Michoacan. See the link for a full report with pictures and addresses. Here's a quick summary:
Ochoa: One of my favorites in all of Portland metro. Great birria de chivo. The only lengua I'll eat. Best huaraches in Portland metro, a "must have" when you go there. (Attached picture is of a huarache topped with birria.) Carnitas and tamales are among the best anywhere. Outdoor grill and al pastor spit. Excellent prices and free help-yourself chips with a rotating group of tasty and distinct salsas.
Maya's: Whoever is running the restaurant in Su Casa seems to have changed hands. Menu was always a little too much Tex-Mex, but that'd be fine if the execution wasn't so poor. The average taco truck was much better. But now they're quite good. Meats are cooked correctly with extra char on most. Everything is well-seasoned. They're also the only place to regularly have uchepos that I know of. Mariachis on Sundays.
Flor de Michoacan: I watched them make gorditas by hand at last year's Cinco de Mayo. Their masa antojitos are made by hand at the restaurant, too. Gorditas may take a while, but they're worth it. Tortillas are pressed and freshly cooked also. Taco fillings aren't great, but the tinga (in this case made with beef) is pretty good. And it's not easy to find in Portland, unfortunately. Very light and crisp chips with an okay table salsa.