With carved wooden chairs, a colonial ambience, and eight decades of ser- vice, La Fonda has a rock-solid following. The kitchen accommodates diners who insist on the “Old #7” (a chalupa and a cheese enchilada), but owner Cappy Lawton’s menu has migrated south. Now you’ll find roast cabrito, nopalito salad, and a pristine scal- lop aguachile. On a recent visit, we were transported by robustly red enchiladas de mole xiqueño and rich duck tacos that one might imagine eating near the floating gardens of Xochimilco. (2/13)