There is a shuttle bus that runs frequently (every half hour I think) from YUL to downtown. You can then take a shuttle bus to most area hotels. The fee is 12.00 one way, or 21.75 round trip. Link to L'Aérobus
If you take the taxi, the fare should be $31 each way.
Public transportation is difficult at best.
Shuttlebus (4-4-4) repeat: yes
Public transport (1-1-1)