suggestions please:)

hi everyone would love some advise on whats best to plant along my perimeter fence to form a natural screen. I have great neighbours but the fence between our gardens is really small 3 foot in height i think. Anyway i would love a bit more privacy. Putting new fence posts and panels in isnt possible (money,time, a lot of hard work etc)plus they dont seem to mind the low fencing.Anyway i was looking for something that may grow to 5 foot look pretty and flowers? any suggestions?