Hey if you're still interested in going one of my profs is asking for volunteers (setting up exhibits, helping out seminar speakers, etc) for the 20th and the 22nd. I believe the "work" is from 9:30 till 5 or so. And there are "off duty" periods.
But anyway...if you volunteer you get in free for all 3 days. If you want to go to the dinners you still have to pay but other than that and parking, you'd be good to go.
I'll be "working" on the 20th and possibly flitting around on the 21st.