1. In a 6- to 8-inch frying pan, shake almonds often over medium-high heat until lightly browned, about 7 minutes. Pour from pan.
2. In a large bowl, mix vinegar, oil, sugar, soy sauce, ginger, and mustard.
3. If peel is tight on mandarins, use a knife to cut it and white membrane from fruit, then cut between inner membranes to release fruit segments. Discard peel and membrane; reserve juice for another use. If peel is loose, pull off and discard, then separate segments. Pull off and discard any loose membrane. Add fruit to the bowl.
4. Peel and pit avocados; thinly slice into the bowl. Mix gently.
5. Add lettuce and almonds to bowl. Mix gently, adding salt and pepper to taste.
Up to a day ahead, toast nuts and make dressing; cover and let stand. Chill greens. Peel and segment mandarins up to 6 hours ahead; cover and chill. Or, instead of fresh fruit, use 1 or 2 cans (11 oz. each) mandarin sections, drained.