Why is it Americans are so frightened when an ethnic restaurant promises to offer specialties of its homeland, then does? It's right there on the sign and menu at El Tlacoyo: "cuisine of Hidalgo," a state in east-central Mexico. This means scary-to-most-of-us goodies such as cheese crisp with brain, cactus soup, pork stomach tacos, beef head burros, head cheese tortas, marrow guts tacos and barbecued goat. A lot of this stuff is actually quite good, once we get past knowing what we're eating. Cactus soup is a marvelous orange broth with nicely bitter grilled nopal. Tlacoyo is a delicious casserole, layered with slabs of masa, queso fresco, white meat chicken, sour cream, cilantro and onion. And we're almost embarrassed to admit how much we enjoy goat -- mild, moist, barely gamy, and more smoothly flavored than beef. But if quesadillas con cesos (brain) causes a cringe, choose a more familiar authentic dish: whole-fried fish smattered with garlic and served with fries, rice, beans and tortillas. Whatever we choose, at El Tlacoyo, it's authentically delightful.