I am rather fond of the relaxed, not-excessively-neat look created by having ad-hoc washing visible. Occasional airing of a doona over a balcony rail would not bother me at all, but routine draping of washing might be rather better dried and neater if on a clothes rack or line within the area of the balcony. Certainly I think a clothes horse drying rack on a balcony is inoffensive. If the outlook on that side of the units is to just to a mostly utilitarian area of carports, then I would be even less bothered by the sight of some washing.