You and I have the same conditions for flowers, but I am having great success with "tiny mice", which has red and purple flowers that cascade, red monarda for height; and yellow and white lantana. I only get sun after 1 PM. I have a pot of black and blue salvia that the hummers adore. I just bought an autumn joy sedum that I'm hoping will bloom because the hummers and bees are all over its partially open buds. I also have a window box of purple and red petunias and cascading geraniums. These are not as popular with my birds but they do get activity and do well in my less than ideal site. May I suggest that you can make a minimum investment and perhaps get some hummers to come right now. The absolute best thing I've found is my small hummingbird feeder, called a humzinger, it's a flat red plastic disk which I have to fill on an almost daily basis to keep up with the demand. I have put it in the window box on a wooden dowell stuck down in the soil so it sits right on top. It gets so much activity I'm convinced the birds would come even if I didn't have flowers. This is only my first year to have hummers so I'm no expert, but I have become a nut over these tiny, curious little birds that are so tame they even come to the feeder when I'm out there on my itty bitty 4x8 balcony.

The only activity I get in my windowboxes is with the annual Salvia splendens, but I'm getting good activity on the Salvia "Lady In Red". You could also try Salvia "Forest Fire", which I'm growing in the ground as well as a hanging basket. Or try a small pot of Million Bells. Also some trailing lobelia might work, along with the salvias. Unfortunately, most of the above need alot of sun, but the lobelia might not need much at all...