My wife loves the friojoles charros at el pique, but, we have found the Tacos al Pastor at Mr. Taco to be our favorite so far. We had a cab take us there and then we waked back in to the square area afterwards. FYI the cab driver grabbed a couple of Tacos to go after dropping us saying they were his favorite as well.If we're counting taquerias as "restaurants," then hell yeah to El Pique. We love their charro beans.
A side note, La Casa del Mojito on 5 has great food. Tostones are excellent and their Cuban Sandwich is dynamite.