Gary I.
Yelp
Nice neighborhood market for Mexican-Latino products.  Since it's a carnicería, they pride themselves on having a butcher shop, "Especialidad Cortes de Carne al Gusto/Special cuts of meat to your liking".  Clean, brightly lit w/ selection of fruits & vegetables frequently used by Latinos.  Also there are canned & bottled goods of Mexican comestibles.  
I have only come into Don Juan functioning as a Taquería.  Selection consists of beef Carne Asada, chicken Pollo Asado, pork Carnitas, marinated pork Al pastor, Mexican sausage Chorizo, pork stomach Buche.
1)  There is a special offer of 5 chico/small tacos for $5, but you have to buy all of the same kind.  I ordered the Taco al Pastor/shepherd which is not made from lamb as indicated by its name but made from pork that seems marinated in a sweet, salsa de chile Colorado sauce w/ what seems like dark Worchester sauce for a sweet, fruity, fermented lightly funky flavor.  
The pork is of good meaty quality w/ very little fat.  However, the flavours seem a bit flat as though there were no meaty fond de cuisine/broth to add a richer, meatier Umami.  However,  I have eaten far worse al Pastors in other taquerias.  
2)  Also have tried their Carnitas which is basically salted & roasted in  its own juices much like the French style Confit.  Cooked to medium well, but still retained moist soft texture.  For me, I would use fresh Pico de Gallo or some other fresh salsa to enliven the meaty, roasted pork.  
3)  Costillas de Puerco was braised in a mild, sweet, red chile salsa.  Since the pork was cooked for a long time, it was falling off the bone soft & tender.  The fat that came out of the pork dyed a fiery orange red could be called a Mancha Manteles/table cloth stainer in practice if not in real culinary terms.  
For me, a bit of piquancy from more piquant chiles would have been a good contrast to the meaty, fattiness.  Again, there was a lack of strong fond de cuisine to add more of a brothy richness.  Costillas de Puerco would be a good filling for tortillas to make a good taco w/ addition of chopped cilantro & onions. 
On weekends, there is a space in their parking lot to set up a bbq for roasted chicken al Carbon/charcoal.  Small eating area inside the market but not for large groups.  
Overall, the food here is a solid 3+ Yelp stars.  Nice place to get some Latino products as well as a quick bite to eat if you live in the neighborhood or passing by.