The trial for the co-owners of Mexican restaurants in Waterville, Westbrook and Biddeford charged with hiring illegal immigrants will head to a jury on Monday. Both sides wrapped up their cases Friday in Portland for Guillermo and Hector Fuentes. The brothers have pleaded not guilty to the federal charges. They were arrested more than a year-and-a-half ago after agents say they found illegal immigrants living in the basement of the Fajita Grill in Westbrook. We’re told they discovered evidence of illegal activity, as well, at the Cancun Mexican restaurant in Waterville and at the Cancun Mexican restaurant two in Biddeford.The two men are also accused of helping workers get fake social security cards.