Prepare elbow macaroni according to package directions. Drain and rinse under cold water; drain again. Toss with oil, cumin, and salt. Layer macaroni, beans, corn, bell peppers, and onions. Place in a 9" x 13" pan. In a mixing bowl, combine mayonnaise, sour cream, and taco sauce. Spread mixture evenly over top of pasta, sealing to edge of bowl. Cover tightly and chill overnight.