In addition to searching reviews on our website, GlutenFreeTravelSite, for informative first-hand travel and dining feedback from others on gluten free diets, it's a good idea to contact a support group in the area you plan to travel. Many times they will be able to provide you with a list of Celiac-friendly restaurants and grocery stores that offer gluten free foods. Here's a list of the well-known Celiac associations, both in the U.S. and worldwide...their websites have contact information and often list support groups/chapters.
National Celiac Association: Incorporating the former Celiac Support Association, NCA provides educational materials, works with industry and the government to improve labeling practices, and offers a Recognition Seal certifying products as Gluten Free.
Beyond Celiac: In addition to promoting awareness and having numerous valuable resources for Celiacs on their site, this U.S.-based foundation has a very helpful list of Celiac Disease support groups around the world.
Gluten Intolerance Group (GIG): They are involved in advocacy as well as GF certification and accredidation for products, food services, and restaurants. They include contact information for their local chapters in the United States.
Canadian Celiac Association (CCA): Provides information on sources of gluten free food, fosters research, and encourages mutual support among Celiacs. They list local chapter and support group help throughout Canada on their website.