Gluten Free Eating

A family member is coming to visit us and he has learned recently he has Celiac Disease and must adhere to a strict gluten free diet. My 'restaurant Espanol' is pretty good but how do we ask which foods are gluten free and can we be sure that the waiter and kitchen staff will understand his needs? Does anyone know of restaurants that have gluten free items on their menu? Any suggestions would be very much appreciated.