The county erected a monolithic, 10 foot, concrete sound wall in my back yard. I read an article about stucco failure because of poor moisture management on a frame house. Can I put stucco directly on this concrete wall without concern of moisture weakening the bond?

You can stucco the concrete wall but you are going to need to apply Galv stucco wire for the stucco to stick.

Stucco will stick to a clean block surface but not to a smooth surface like a concrete wall.

I would suggest concrete staining or an acid stain.

Not sure if stucco is the look you are set on.

YouTube - Concrete Driveway Staining.wmv (http://www.youtube.com/watch?v=cV_YbUuNCY8)

I agree with the advice given but here's one more piece. That wall is not on your property and is likely owner by the county. Ask what they will allow you to apply to their wall.