One place I enjoy is El Moctezuma; it's a Oaxacan restaurant just south of the resort district on Harbor Blvd. (corner of Lampson and Harbor, in a U-shaped plaza. They make a fantastic clayuda, which is a huge, pizza-size crispy, thin tortilla spread with pork-fatty black bean paste, then topped with shredded cabbage and quesillo (tangy, delicious Mexican string cheese). You can get pieces of meat on top if you like, such as tasajo (dried beef) or cecina (chile-marinated pork).
12531 Harbor Blvd., Garden Grove.
El Moctezuma Restaurant
809 N Fairview St, Santa Ana, CA 92703