You will be able to get on the path from the River's Edge Convention Center anytime that it is open. The day we went we couldn't get on there so we went into the lobby of the Sunwood Inn and took the elevator down to the B floor. It was a short walk through the parking ramp.
I'm not sure just how long the Riverwalk is but it didn't take us very long to walk to the end from the Parking Ramp. We then turned around and walked it back up to where it ends on 3rd Ave. (If you keep going you can eventually hook up with the Beaver Island Trail.)
Heading back on the trail towards the Convention Center, Sunwood Inn and eventually under Division Street to 3rd Ave.
It's a very pretty walk along the Mississippi. We saw a mink below on the shore and as we walked saw evidence of a beaver's work.
One tree already gone.
It was very quiet the afternoon we walked along the trail. There were two bikers that passed us going pretty fast. It's a nice addition to downtown. The only thing I would suggest to City personnel would be to mark the trail.