I'm a firm believer in only ordering things that you can't cook or are cost prohibitive to prepare yourself. Lengua and true cabeza both fall into that category for me, especially as a single person - I'm never going to be able to cook a whole cow's head in my apartment oven.
Because of my rule, when I get tacos, I prefer to get lengua. Last night (2/22/14) I grabbed a lengua and a cabeza taco for the UYE Tacolympics.
Apart from the cost, which is a decent price, the tacos are bland. The meat is diced rather than shreaded, which in turn makes less flavorful tacos.
The cabeza was straight up dry. The tortillas weren't warmed or anything. The salsas didn't add much except in terms of volume. Meh!