I am definitely seeing them on the ground within a few blocks of the needle exchange in Ithaca, NY and this is something that's become noticeable in the last few years. It's part of a general coarsening of urban life, where it is not unusual to hear gunshots at night, you hear about fatal stabbings just a few blocks from where a friend of mine lives downtown, etc.

Where in Boulder are you finding needles? I'm yet to see one after ~4 years here, but I've mostly stuck around CU campus and Pearl and the surrounding areas. Plenty of discarded vapes everywhere, though.

Boulder Creek is the most glaring spot, but you might have trouble finding them until the homeless campers tents are forcibly removed once every 9 months. Scott Carpenter is another good spot. Park East Park is where the aforementioned kid was pricked.

I drove through Boulder and Boulder Creek.. it didn't seem like a happy place.

Denver, OTOH, seemed quite cheerful.

Did I get a proper impression of each or anecdotal anecdotes?

Anecdotal I'm afraid.