Hi Bob,
From my past experience most, if not all, attendees get there on Friday. We do most of our riding on Saturday morning, and we start pretty early.
I have, however, waited until after rush hour to leave the city in the past. Of course, that means arriving in Galena in the late hours of the evening, but it was worth it for me to not have to deal with the traffic/hassle (once you're out of the city limits, though, traffic is pretty light).
This year, I took the day off of work and am leaving early in the day, though I know that isn't an option for everyone.
Ride sharing is set up just like this....via the forums and facebook: connecting with other members.
You should have gotten an email earlier this week with your housing assignment and and a Google Doc link for food sign-up for the party/BBQ on Saturday night.
Feel free to reach out to the people included in the email list for your house to coordinate groceries and the like!
Let me know if you have any other questions---looking forward to a great weekend of fun and riding!
Rita