Hi ridealot,
I've lived in Cincy for 20 years now. I used to commute from Clifton to a job on the KY riverfront inbound at 2-3pm and home at 2 am while in college. Sometimes Vine street was dicey but I'm still here. All the advice so far is great. What the other guys don't know is that almost all the roads out of downtown are uphill and in not quite nice neighborhoods. I found that most of the morons are on foot and a)didn't hear me comeing or b)didn't care I was there. I rode a uglified bike with a t-shirt and shorts to not attract attention. Also, I found Central Parkway to be better lit and less populated by scary people at dusk. It doesn't hurt that the cop cars are parked there most of the time.
Are you doing the Morning Glory ride this year? It's probably my favorite short ride around.