Because Brussels is the capital of the EU, the city is very diverse. When you sit on the tram, it is completely normal to hear three or four different languages. Therefore, being foreign isn't an out of the ordinary thing. We do stick out like sore thumbs however. We have found the public transportation buses and trams to be extremely quiet. However, the students in our group are very much the opposite. Speaking English in our normal tone is quite loud compared to the people of Belgium.
Another blatant way we stick out is our dress. The combination of a north face backpack, iPhone, sperries, Michael kors anything(watch, purse, wallet) and reusable water bottles usually gives you away. However, against popular belief, Europeans do wear leggings. I would stay away from bringing a bright color rain coat because our group looks like the rainbow when we walk down the street and rain coats are rarely worn by locals.