El Dorado Spa Resorts & Hotels and Azul Hotels by Karisma launched a "Four Diamond" summer promotion for customers who book a minimum four-night stay by July 9 for stays June 15 to Aug. 31. Under the promotion, guests will receive an upgrade to a suite, a $50 spa credit, a $50 dining credit for a dinner on the beach, a $50 credit for wine purchases and a $50 credit for a tour of Chichen Itza.