Downtown, near the Embarcadero, is the most centrally located of San Francisco's dim sum restaurants: Yank Sing. Tucked away on the ground floor of the Rincon Center (an old U.S. Post Office), this restaurant is always buzzing with hungry crowds. Servers dart between tables with carts full of treats: shrimp dumplings, grilled bok choy and fried chicken feet, a house specialty. To drink? Chrysanthemum tea, of course. Just about the only downside is the price-a recent visit with a buddy cost $78, including tip. That's spendy for dim sum. Still, every food fan should experience the joy of Yank Sing at least once.