Come the lunch hour, even on summer days when highs look way down at 100 degrees, the blue canopy outside this modest food truck on 16th Street shades quiet crowds at foldable tables. They are regulars, and many are eating tacos. Choices are scrawled on paper taped by the ordering window. You would do well to stray from more typical offerings like carne asada and into the offal and odd bits. Buche, pork stomach, is soft with some spring and radiates warm porcine goodness. A pile of tripas is blistering hot and crackly, the savage crunch giving way to fatty richness cut by creamy avocado salsa. But nothing matches the cabeza taco, hunks of pillowy head meat at once decadent and reserved, adorned with raw onion and chopped herbs. This one is so perfect that adding salsa almost feels like a crime.