I lived here for three years. When in doubt about the language speak english. You could be offending someone if you speak french in the belgian section and belgian in the french section. There is a clash between the languages. So if you speak english, use it. Until you know for sure. You will be surprised at how many of the people speak english. Very, very friendly people, who will open there homes and hearts to you, especially if you get away from the main tourist areas.