Worse months for weather January-March. Outside those 3 months, there are 1 month in autumn or spring (usually not both) that completely sucks: November and April are good candidates the other ends up being a tossup (could be good or bad).
Late february and March are the worse from a psychological point of view, its dreary and winter is starting to wear you down.
The "good months" are usually May to October.
December is slightly cold, but it doesn't rain, there's a little snow and the pre-holliday atmosphere is great. So, I'll add it to the good months.
(So, its 7 months that are good).
The city of Montreal itself is very progressive, its like a gay and TS heaven, the rest of the province, not so much. You can pass or not pass in the central neighborhoods, people won't blink.