One of the things you can do is go to restaurants that are popular with the locals. Use google translateGoogle Translate to find sites that show where locals like to eat. For example, "best restaurants in buenos aires" = "los mejores restaurantes de buenos aires". Search for that in Google and Guiaoleo shows up, which is a Spanish language review site for Buenos Aires restaurants. The top restaurants there will be different than the ones you find on Tripadvisor TripAdvisor.
Don’t be intimidated if they don’t have an English menu. Write down the words for fish, chicken, vegetarian, etc., before you go. When you’re ordering, just point at items on the menu.