Nice!!
At our Denver rally, scheduled from noon to 4 pm MDT, it was a bit toasty—low 90s and bright sunshine. My wife and I were there for the first couple of hours looking around then marching with the rest of the crowd (I’d SWAG a few to several thousand).
When we got a little too warm, we’d go sit in the shade of the tall buildings or trees and cheer for the passersby. Then we’d cycle back in for a while. It appeared that others were doing similarly, and there were volunteers handing out water bottles or granola bars to any who needed them. (We brought our own drinks.)
The only real injuries we saw were to an older (than me) looking fellow who misjudged a curb/center island and fell awkwardly. Several of us were on him immediately and he said he was OK, just a little banged up and bleeding from his scrapes. Others served him some water and tried to move him into the shade while dressing his wounds, so we went on, seeing he was already in good hands.
There were very few police that I saw on our route, mostly for traffic direction and blocking off certain streets. We saw more fire fighters and paramedics and no one seemed to be in any distress that I saw.
As others have reported, spirits were high, with lots of camaraderie and supportive, joyful (but appropriately angry) atmosphere. All races, old and young and everything in between, lots of American (including mine(!), with probably 50/50 flying upside down in distress) and other flags.
A very terrific event and my wife noted that she found another scheduled for later in the afternoon/evening! (We didn’t make that one. 
)