At Sylvia's I was the victim of gross racial profiling. When asked how the carne guisada tacos were I was told "Have you ever had carne guisada?" And then, "it's good".
What he meant to say was the carne guisada is unremarkable.
I ordered 3 tacos to get a nice cross-section of their offerings.
Bean & cheese: skimped on the cheese. At first we thought perhaps there was a bed of cheese beneath the beans (beans were good, by the way), but there was definitely a cheese shortage.
Carne guisada: bland and not enough filling. As agdev01 mentioned, the tortillas are homemade, and good.
Chilaquiles/Christmas taco: great flavor but again skimped on the portions.
Their salsa was tasted alright but was not hot. My one regret is that I didn't try their barbacoa, because on a Facebook fan page for San Antonio tacos the owner had posted that they have the best barbacoa in town. Perhaps that's why their other tacos are mediocre - their focus is 100% on the barbacoa.