Cook macaroni according to package directions, omitting salt and fat. Drain and set aside.
Bring 3 cups water to a boil in a medium saucepan. Add shrimp; cook 3 to 5 minutes or until shrimp turns pink. Drain well.
Combine macaroni, shrimp, cauliflower, and remaining ingredients; toss gently to combine. Cover and chill at least 8 hours.