Yes, there will usually be a lot of people going to the track even on Friday. Our Friday’s seem to resemble many other tracks qualifying sessions from TV (attendance wise).
How long does it take to get to the circuit?:
-From your hotel if you take the metro it would probably be 15-20 minutes or so. Depending if you need to switch metro lines (different colors, see the map/picture in the link)
You need to get off at the Parc Jean-Drapeau exit. So you guys need to take the YELLOW line (it will be the same exit if there is a Thursday open house at the track)
****There is one more way to get to the track*****
Very few people know this route. It will save you a lot of time after the race & quali.
This a ferry that leaves from the old port & goes to ile sainte-helene (same connecting island where you would get off on the metro/subway). F1 weekend there usually a boat every 30 minutes. It costs 15$ per day for a round trip. The ride lasts about 10-15 minutes. You will get a chance to take great pictures of the Montreal skyline.
You buy your ticket at the booths in the old port near where you board the ferry.
As you can see the ferry lines are in between The Jacques Cartier Pier & The King Edward Pier. Which is also where you buy your tickets.