My first observation is: The 606 is packed! Depending on the time of the day, just like peak hours at a gym, the 606 can be crowded. I'm talking bikes, runners, walkers, unicycles and plenty of dogs! (OK, no unicycles…yet!) If you have a friendly dog, you're in luck because you will meet and you will greet. Lots of folks will want to pet and interact with your dog. If you have a shy or skittish dog, I would say be careful and try your best to avoid peak hours. It seems peak hours on the 606 are anytime on the weekends and the early evenings. I have been up there a few mornings and it doesn't seem to be that crowded.
This is a big one: If your dog has a tendency to lunge at bicycles or skateboards, be aware and be safe and make sure you have your dog away from passing traffic as bikers do come up fast and the trail is not that big. The potential for an accident is definitely there so practice proactivity and keep your dog on the blue foam lining that runs along the landscaped sides of the trail.
The 606 does enter and exit at Damen Ave. and Churchhill Ave. so if you want to stop by the Churchhill Dog Park, you're in luck! We made an unplanned stop there today and the dog park was not overcrowded, but there were enough dogs there to be entertaining for any dog stopping off the trail for a play session. The doggie pool is out and the water is turned on so your dog is free to take a dip on a hot day as well!
The 606/Bloomingdale Trail is very peaceful in the morning around 8:30 or 9AM. If you want to introduce your dog to this new Chicago-spot, that would be a great time to do it. I should add, there are no dog water fountains that I have seen so far, so come prepared either with water or use the human water fountains located about the midway section of the trail.