Hi there...Sue, you're right, it's usually a zoo at the start...and I am sure that you're probably already aware, but Cascade is having the start line (and parking) on the East side of Marymoor park this year; I think that the Cirque du Soleil presence as well as other events is figuring into that change.

Whatever it is, it's best to not even go near the West Lake Sammamish Parkway entrance to Marymoor - unless, of course, you like sitting in traffic gridlock

here's the info, map and directions from the Cascade site:

http://www.cascade.org/EandR/flying/FW_Details.cfm

It's going to be a gorgeous day - ride safely and have fun!
Mary