Flower buds for spring bloom are formed in the summer and early fall. If this area is in really dense shade, bloom will be significantly reduced. Direct sun in the winter is pretty hard on rhododendrons and azaleas as well. Winter sun, especially when combined with low temperatures and wind, can and does do serious damage, especially to evergreen azaleas. It might be worth trying one or two azaleas in this area to see how they do - protection from winter sun and wind with burlap or other type of screen will help a great deal - but I certainly wouldn't commit to an entire hedge without a trial planting.