On mostly all of the organized rides I've done (and that is at least a dozen every year) the routes have been fairly well marked, and unsafe intersections have had volunteers or police officers directing traffic.

I'm participating in this ride in my area and I am going to be one of the sweepers to stay with the slower riders. I'm not sure if this was something that our local organizer thought of doing, or if it was suggested by the Trek people. Perhaps you could check with the shop sponsoring the ride in your area and see if they are going to have volunteers doing that as well.

Our local organizer is expecting many more less experienced riders than on other rides so I don't think you'll have anything to worry about.

P.S. I also had trouble registering until today.