CPD usually has traffic-related comms on their traffic talkgroup (56151).
As with most other big events, parades, Browns games, and the like, check one of the many interop/regional talk groups. They seem to like Regional 4, 9, or 10 for such events but the actual talkgroup seems to vary.
There may also be other traffic on different systems, such as Downtown Cleveland Alliance 464.075 (DPL 032). This is a good frequency to keep in for regular downtown listening.