I agree with Rebecca. I didn't do Orcas, but we really enjoyed riding on San Juan Island, once you get out of Friday Harbor. We did 3 rides, and we took the shuttle to the English camp and hiked up the hill there, which was also awesome. Maybe I didn't know what to do on Lopez, but it just seemed like there was nice scenery, but not a lot of stopping places. I think we ate at the same restaurant as Rebecca.
Overall, while the riding was pleasant, the roads were chip seal (my first experience with that), which I didn't like, even with my titanium bike. I find that I don't really like riding in beach areas (anywhere) in the summer and I avoid it like the plague around here. Too many people, especially the ones who don't know where they are going.