Beef, thanks. I'm up there frequently and said I'd document the tacos scene, but alas never got 'round to it. Your coverage is good.
I've mentioned some of this before, but I'll repeat so it's easy to find:
The Supermercado I agree isn't tops for tacos, but it is notable for a few things. The house made slasa and guac are actually made to order, as in an old abuelita typically dices tomatoes, onions and cilantro when you order. During busier periods they sometimes have a batch pre-made, still good. The abuelita also makes fresh
requeson, which I've enjoyed a lot. Basically Mexican ricotta.
La Perla is a very cool place and serves lots of functions for the migrant labor force in SW Michigan. It has the best tacos, particularly when the outside stand is up and running and the teenage kid is manning the griddle and trompa. La Perla has a vast array of tortillas trucked in from Chicago, but also from Grand Rapids and K'Zoo. Probably the best flour tortillas I have had outside the Southwest come from Las Brazas, which I believe is in G.R. or Battle Creek. When fresh, they are the best. But they turn quickly - flour, lard, and no preservatives. My favorite thing about La Perla is the selection of Yucatecan items, particulalry achiote-based pastes and rubs, plus bitter orange etc. for cohinita pibil. These things can be tough to find even in Chicago and are a great resource for those who roast pigs in their backyard, like I do.
Changing gears, I saw you are doing a perch crawl. I'm a huge perch fan and always eat it out there. The range is vast, from horrible (Zeke's in Dowagiac) to sublime (Thirsty Perch in South Haven, Clementines in S.H. and St. Joe, and, improbably, BT's near Sister Lakes). Keep up the good work!
PS, I should mention that La Perla has an interesing assortment of Mexican breads and pastries - most notably for me a good, anise-tinged cemita/semita. Throw some of the house made carnitas one one of those and you've got a good meal.
Last, the Supermercado is the place to get well-seasoned, well-machined arrachera for the grill and menudo on the weekend. They also make cecina, which is the taco filling of choice there.