1. Cook pasta according to package directions, omitting salt and fat. Drain and rinse under cold water; drain.
2. Heat a large nonstick skillet over medium-high heat. Add beef to pan, and cook 3 minutes, stirring to crumble. Stir in garlic, and cook for 2 minutes or until browned. Stir in noodles, carrots, and the next 4 ingredients (through mint). Combine juice, sugar, and soy sauce in a small bowl, stirring until sugar dissolves. Add juice mixture to beef mixture; tossing gently to coat. Arrange 1 lettuce leaf on each of 4 plates; spoon 1 1/4 cups beef mixture into each leaf. Top each serving with 1 tablespoon peanuts.