Another good thing about the road markings is that if there is a bad section of road the pot-holes are marked, making them easier to avoid.
I can only speak for myself, but, I would not mind sharing the road on a tour with some moped-ers. (The bike ride organizers might disagree.) If you do sneek in on a ride make sure to follow tour riding ediquite, including telling the bicyclist that you are "on your left" when passing them on the left. And indicating verbally indicate that you are stoping.
Also if you decide to sneek onto one of these tours do not be surprised if some bicycle-ist try to pass you, and succeed. Also, if you have a group of bicycle-ist follow you closely, talk to them and keep a steady pace, and do not ride squirely. These bicycle-ist would be drafting off of you, essentially using the hole that you punched in the air to cut down on the air resistance that they have to face.
You might also think of joining the ride rather than seeking on. This would entitle you to eat at the rest stops if these are included on the ride. And may entitle you to "sag" services. (They help out worn out, and broken down riders, and gives them rides back if things get way too bad.)
You might even consider volintering in helping out in some way with the ride. Perhaps taking along tools, patch kits, and a pump to help out the "sag" service.