I think these coupons are rare.
"Enter your information to receive a Buy One Get One Free Entrée Offer (one offer per account) for one of our Signature Dishes or try Pei Wei’s NEW Thai Chicken and Korean Steak Lettuce Wraps with your favorite Coca-Cola Freestyle beverage.
Promotion ends October 13, 2013. Offer expires October 20, 2013."
Pei Wei Locator: https://www.peiwei.com/locations/locations.aspx