Thanks guys for your replies. We'll need to chat about it and see if it will be on our summer agenda. We tend to prefer riding in the mountains and longer climbs but the coast and coastal range are scenic too.
Know all too well the disappearing shoulder situation. Have had it on a commute many years ago that made the last mile a crap shoot. Had the shoulder disappear one day for a good long stretch in that ride we did in Colorado with fairly heavy, and not real friendly, highway traffic.