Not sure about the Alpine Choughs. Only seen Red-billed in that area.
The track North from Marchenilla is where I first saw Rufous Bush thingum. And indeed on prickly pear, not far along the track. If you then carry on past the rock / stone stuff compound on the right, which was moved here a few years ago as it was un unsightly mess near the main road, you go up a hill and about half way down on the left in the little dry valley is the best place for RBC. The track also used to be good for Black-eared Wheatear, but they seem to have moved away in recent years.