Lots of bicyclists without bike helmets in Montreal. I'd guess helmets are like 50%, though I haven't really counted. Common, unlike Osaka or Amsterdam, but not as ubiquitous as I recall from the US. Some of that is people on Bixi bikeshare, but I've seen road bikers in traffic without a helmet. There did seem to be more helmets yesterday on the canal shared path, but that's the sort of thing that probably attracts faster biking (apart from having to share with the pedestrians.)
More bikers than I was used to in LA, not sure about Boston or Oakland. I see a lot on Maisonneuve but it has a physically protected bike path.
Montreal forbids biking on the sidewalk, unlike LA. The one sidewalker I recall seeing was laboring uphill toward Mont Royal. Can't say as I'd be happy to bike on the major streets here. See the DW comments at https://mindstalk.dreamwidth.org/582945.html#comments