City Restaurant Week   City Restaruant Week asks you to Friend a Chef as you try the many offerings by the talented chefs of downtown and the riverfront from April 27 to May 2.   The week will feature $15 two-course lunches and $35 three-course dinners. In addition the 10 restaurants will offer a special Chef's Table on Monday night and the ever-popular Dine Around on Saturday night of the week.   The participating restauarants are: Ameritage Restaurant & Lounge, Cafe Mezzanotte, C.W. Harborside, Deep Blue, Harry's Seafood Grill, The Green Room at Hotel DuPont, The Exchange, Mikimotos, Washington Street Ale House, and Orillas Tapas Bar & Restaurant.   For more infromation, visit www.cityrestaurantweek.com.