What part of town you coming from? That general area is pretty quiet but it’s hard to get there without going through a busy section. I live downtown (Belltown) so I very quickly adapted to riding in traffic, but since I have an automatic scooter I had it easy.
I wouldn’t stress over trying to make this practice session, I would focus more on getting your own practice in. I’m not entirely sure how this big session will go as this will be my first time doing this. While I regularly stop by and do a 10 or 15 minute practice session, I might be bored with a large group practicing for a couple of hours. But I have to confess I am secretly looking forward to watching folks attempt the box. It will be interesting to see the skill levels on show.