We finally found the roadrunner nest, and they are sitting! I knew it was somewhere close to the house, but was surprised they picked this spot. It is a popular location, surprisingly, because it is not a quiet or secluded one. It is right next to the garage, on top of the potting shed, but under the house roof. And the garbage can is stored right underneath. It is protected from all but enterprising snakes, but I thought that might not be that important to the roadrunners.
The last couple of years the curve billed thrasher pair have raised a number of families in the same location, as a matter of fact it is their nest that is being used - prickly and sticky as it is. There is also a Say's phoebe that built a nest underneath Roadie's, in the garbage can storage itself. I am afraid she may have had to relocate her nest too. A bit too close for comfort with a predator upstairs.
Unfortunately we do not know how many eggs are being hatched; our mirror-on-a-stick is the wrong angle for this so well hidden nest. We did find an egg on the driveway that was roadrunner sized, but no embryo had formed yet, so perhaps the egg was deemed "not right" by the parents. Stay tuned.