As reported by the NYTimes, here's what the CDC is now saying (emphases mine).
Everyone can do without a mask when …
■ Walking, running, hiking or biking outdoors, *alone or with members of the same household*.
■ Attending a small outdoor gathering with fully vaccinated family and friends.
*Fully vaccinated people* can do without a mask when …
■ Attending a small outdoor gathering with a mixture of fully vaccinated and unvaccinated people.
■ Dining outdoors at a restaurant with people from several households.
For these kinds of activities, *unvaccinated people* should still wear masks and maintain social distance, the C.D.C. says.
*Everyone* should still wear a mask when …
■ Attending a crowded outdoor event, like a parade, sporting event or live performance.
I'm always wearing a mask outside here in NYC, but mostly for convenience: Once it's on I don't have to think about it. (Plus it's a help on cool days, of which we're still having too many.) I also have it on in my workouts, but those are walking and only rarely does my pulse go above 150bpm. I tentatively have a marathon coming up in a few months and, as someone suggested above, I'm hoping to be a little "supercharged" when I do the marathon with no mask--though it may be more of a psychological than a physiological boost.
TL, DR: Here in Manhattan I see a mix: Maybe a majority are without masks, but a signficant (and somewhat surprising, to me) fraction have masks over nose and mouth.