Montreal is a French city -- the largest French-speaking city outside France. Bracketing your English with an opening Bonjour and a closing Merci is not only good practice but a courteous gesture. Don't worry about your accent; plenty of Montrealers are not pure laine native speakers themselves.

Almost all Montrealers speak excellent English, which can be a problem if you're trying to learn French. It's hard to get two sentences out before they switch to English on you. However, if you can clue them in that "Je suis un Américain", they'll be quite impressed that you're trying and will help you out. Otherwise, they think you're an Anglophone Canadian who never bothered to learn French, and they have no patience for that.

Also pay attention to where you are. Although Anglophones and Francophones are mixed throughout the island, generally the Eastern half of the island is French and the Western half of the island is English. The conference is located almost smack on the dividing line (which is quite fuzzy, and not really much of a line). Although almost all Montrealers speak excellent French, many of them around the conference center and points West are not native speakers, and may well prefer English. I suspect natives are able to tell who prefers which language, but I can't.

Francophones are often far more insecure about their command of English than they should be. I've had more than one Francophone apologize to me for their English in language that to me was indistinguishable from what you might hear in Vermont, and quite a bit better than what you might hear in Brooklyn.

Here are some useful French phrases. Note that Quebecois French is not Parisian French:

French road signs: Voie/Lane; Droite/Right; Gauche/Left (Voie Gauche/Left Lane); Prochaine/Next; Sortie/Exit; Entree/Entrance; Defence/Not Allowed; Interdit/Not Allowed; Stationement/Parking; Vers/Towards; Centre-ville/Downtown; Pietons/Pedestrians; Camions/Trucks; Lentement/Slow; Ecole/School; Paye Ici/ Pay Here; Feu/Light; Rouge/Red; Vert/Green; Ralentir/Slow down.

French shopping signs: A Louer/For Rent; A Vendre/For Sale; Vente!/On Sale!; Vendre/ On Sale; Vendu/Sold; Vente de Garage/Garage Sale; Rebais/Discount; Reduit/Reduced; Couper/Cut; Prix/Price; Economiser/Save; Epargner/Save; Argent/Money; Depanneur/Convenience Store(Tabacco, junkfood, beer); Tabagie/Convenience Store in the Metro; Marche au Puce/Flea Market; Cuire/Leather; Soulier/Shoes; SAQ/Hard Liquor Store; Caisse/Cashier Desk; Ascenseur/Elevator; Escalier/Stairs; Femmes/Women; Hommes/Mens; Enfants/Children; Grandeur/size; Taille/Size; Petite/Small; Grande/Large.