By Emily Green and Herbert Villarraga TIJUANA, Mexico, June 14 (Reuters) - Some 25 miles (40 km) south of the U.S.-Mexico border, nestled between taquerias in the suburbs of Tijuana, hangs a flag in the Mexican colors of green, white and red. But its design is far from common in these parts. Inside is what owner Saied Assadi says is only the second Iranian restaurant in all of Mexico.