Bring 2 cups water and garlic to a boil in a medium saucepan. Add chicken; remove from heat, and let stand 8 minutes or until done. Remove chicken from pan, using a slotted spoon; pat dry with paper towels. Place on a plate, and cool completely.
While chicken cooks, prepare Green Goddess Dressing.
Place lettuce on a platter. Arrange chicken, tomatoes, and next 4 ingredients (through avocado) over lettuce, alternating ingredients. Serve with dressing.