How many hours of sun; how tall do you want it to be? Trailing torenia is a nice low plant that wants some sun. Coleus doesn't have flowers but sun coleus is vigorous and gives you lots of color. Of course you know of impatients which blooms and blooms.

I think I would try morning glories up the fence. I have MGs in a spot that gets pretty much the opposite - morning shade and midday sun, and the MGs often wilt in that hot sun. If I had the opposite situation, I think the MGs would bloom in the morning sun and last longer with the afternoon shade.

Plus they would look so darn good on that fence!
:)
Dee