Here are some options for accommodations near the conference site. You can find many more.
Getting downtown from the airport: Take a cab from the taxi stand, meet an Uber at the Uber stand or take the 747 bus. Buy a bus ticket at the machine inside the terminal for $10 (maybe buy a round trip ticket). Take the bus beyond the first stop at Lionel-Groulx metro station to the second stop (Guy St.) or third stop (Drummond). The YWCA hotel is between these two stops. The bus will be going east down Rene-Levesque and hotel is on the northeast corner of Rene-Levesque and Crescent (north is towards the mountain). On the south side of Rene-Levesque, Crescent is called Lucien-L'Allier, so don't get confused.