As road users they are just as entitled as you to be there. If they happen to go a little slow for your liking, that's unfortunate, but tough. Sometimes I get stuck behind tractors, or in a jam, or a red light.
If the roads are narrow, maybe they are too narrow for a car to pass safely, in that case what's wrong with riding two abreast? It's safer for them and you, it stops overtaking. Think commanding the road.
If the roads are as twisty as you say, and you go round the bend at "moderate" speeds, maybe you're the one driving too fast and possibly in a dangerous fashion. After all you should be able to stop in the distance you can see.
If they assume car drivers will see them, car drivers should see them, through use of good observation, anticipation, road positioning, awareness and appropriate speed. If they don't it could be argued they shouldn't be driving.