There are three qualifications for a true hole-in-the-wall: It has to be tiny, locals-only, and do something so surprisingly well that it earns the lifelong loyalty of its regulars. The 20th Street Cafe hits the mark on all three. First, it's definitely small -- a dozen or so tables and a six-seat counter in a luncheonette-style storefront. Second, no tourists are going to stumble across it while looking for a Denny's, and if they do, odds are they'll just turn up their noses and keep on walking. And third, the food -- from the chicken-fried steak to the meatloaf and mashed potatoes -- is solid, hearty American diner fare so stick-to-your-ribs good that after one taste, you'll never look at a California veggie plate the same way.