Selena Gomez and Benny Blanco. (Allen J. Schaben/Los Angeles Times via Getty Images)Selena Gomez will soon be a Mrs. - she and Benny Blanco are reportedly gearing up to say "I do" at an ultra-private, star-studded ceremony on Saturday, Sept. 27, in Montecito, Calif.While they haven't officially confirmed the date of their nuptials, celebrity guests have reportedly begun to arrive.