While the normal walking on a street with no sidwalks will be to walk against traffic so that Mona can hear them coming from the front, sometimes, this will not be possible or practical.
The guide must learn to find a shoreline no matter what the direction of traffic is. It would also be helpful for her to find crosswalks. Most safe cross walks will have a painted line markings. Not all painted line marked cross walks will always be safe.
On known routes, Mona may make a choice. Cali will have to respect Mona's choice and keep her safely out of traffic lanes.