I ride pretty regularly in the Baltimore Bike Party (look it up on facebook). We have thousands of people who have shown up for monthly themed rides through the city. Some takeaways that I have from the group are:
*Ride through parts of the city you may otherwise not see/dare to go. We regularly ride through some of the "worst neighborhoods" in Baltimore and receive nothing but love from people. Folks hang out of windows, bang on pots and pans and many join in on the ride and have become regulars. I always enjoy riding through the hood much more than the yuppie neighborhoods of Charm City. You'll find that people are less likely to stand on their horns while your massive group clogs the intersection and usually get out of the car dancing/videotaping on their phones as you pass by.
*Set up a good group of volunteers who know how to "cork" intersections if you're not planning on obeying all traffic signals. Your ride will be much faster/enjoyable if you cork, but I wouldn't advise doing so unless you have a good group of people and some experience safely blocking an intersection.
*If you have extra tubes/tools, volunteer to ride at the end of the pack. Invariably someone will ride into a storm drain and get a pinch flat and be left stranded. I've had to borrow tubes and given them away on several occasions
*Cleanup afterwards! We always make sure to clean up the parks from which we start, stop midway and end. The neighborhood cat lady is much less likely to complain to the powers that be if pick up all the natty boh cans people carelessly leave behind.
This is the mayor of Baltimore during the 80's themed ride
wheelies are kind of a thing in Baltimore
encourage lights and helmets!