Last trip I did Chefs de France, Biergarten, Nine Dragons, and San Angel Restaurante. For ambience, San Angel and the Biergarten can't be beat. Chefs de France probably had the best food. Biergarten had a great atmosphere but the food is merely okay. For a group, San Angel might be nice b/c of magaritas and stuff, especially if you can get a table near the river and watch the people on the cruise go by.