I tend to ride out in the lane on a two-lane road like that. I have a mirror so I know what's coming up behind me. When traffic approaches from behind, if the shoulder is clear of debris and other traffic, I will move over to the shoulder to give a car more room to pass. If the shoulder is not safe or clear, I remain in the lane. Around here, cars will generally just cross the double yellow center line to pass in the oncoming lane (even though it's technically illegal).

The default, though, is to take the lane so the motor traffic sees me out there. When it makes sense, I concede the lane to allow traffic to pass. It's a process of give and take. The way I see it, it's better to be out in the lane then move to the shoulder, than it is to ride on the shoulder and pop out to the lane occasionally due to debris, rough pavement, etc., because when I'm in the lane, approaching traffic more actively has to think about my presence.

In terms of communication, taking the lane says to traffic approaching from behind, "You need to change lanes to pass me." Riding near the fog line or on the shoulder says, "It's okay to pass me without changing lanes." If you don't think it is safe for a car to pass you without changing the lane, you need to take the lane to clearly send that message to approaching traffic.