Former Montreal here,
First suggestion, head over to the Otakuthon forums. Being somewhere in the top 12 anime conventions in North America brings a bit of a crowd. Go say hi in the Nouveaux Membres thread (Off Topic section), it's a good start!
Normally once spring comes back, there is usually a cosplay picnic in june and maybe an open photoshoot before that in the area. (GT section normally has those)
There's a group for those activities on Facebook, Link Here
, where it might be easier to see the announcement for those events.
Apart from those events, there is the Montreal Geek Festival that's making a comeback this year, you'll see plenty of everything, from gaming to technology to cosplayers. April 6th (geekfestmtl.com)
The lack of conventions in Montreal in the spring is a little annoying. There's one in Quebec City called Nadeshicon (Nadeshicon.ca).
This weekend many Montreal cosplayers are in Gatineau (across from Ottawa) for G-Anime, it's pretty much the first cosplay event of the year in the province.
And i guess that's it!