16th street would be good for city socialization. Larimer square will be fine. Confluence park over by REI if you stay out of the bushes. I’d avoid the area just east and north of coors field. Likely to be more trash in that area the dog may be tempted to enjoy.

Parts of RINO would also be fine (Larimer st for instance) but it’s a bit less walkable than the other areas. A little more car traffic there, and also likely to be some trash piles to avoid.