Dressing: Whisk together lime juice, cilantro, sugar, chili powder, cumin, salt, and pepper. Add oil in a stream, whisking until emulsified.
Beef: Cook onion, chilies to taste, chili powder, and cumin in oil in a 12 inch heavy skillet over moderate heat, stirring occasionally, until onion is softened, about 6 minutes. Add beef and cook, stirring occasionally and breaking up lumps, until meat is no longer pink (about 5 minutes). Spoon off any excess fat from skillet. Add tomato sauce, salt, and pepper to beef and cook, stirring, until slightly thickened (about 3 minutes). Remove from heat.
Salad: Peel and pit avocado, then cut into 1/4 inch pieces. Spread lettuce over bottom of a shallow 4-quart dish. Spoon beef mixture evenly over lettuce and continue making layers with tomatoes, cheese, beans, avocado, and olives. Drizzle dressing over salad.