I've close the poll! Thanks so much for voting. It ended up looking like this after 409 votes:
San Francisco - 134 - 32.76%
New York City - 115 - 28.12%
Montreal - 112 - 27.38%
Toronto - 48 - 11.74%
I've now made my decision - which was tough. It was also based on flight prices and invitations in my email inbox and stuff like that...
The winner is... Montreal! I booked my tickets today.