How often do you feel like watering?

Also, morning sun or afternoon sun?

Shade/partial sun: Impatiens come to mind. Also coleus, begonias. Spider plants are totally cool in window boxes and will do well.

About watering, make sure you use those expanding crystals: add water and they turn to gel. Mix them with your potting soil and it will cut down on the watering demands. You can usually get them at Home Depot or Lowes. I think it's sold as "Soil Moist".

The windows mainly get morning sun. As far as watering, I usually do the potts once a day in the morning, twice a day in the summer heat. I want to choose something with a lot of color that will fill in and some thing hanging down as well. I was thinking on coleus and potatoe vine but would like flowers as well.

Tuberous begonias come in many beautiful solid colors and there are some with a picotee edge in a contrasting color. Some almost look like roses. Last year I did some boxes with these highlighted with coleus, sweet potato vine (chartreuse or burgundy, depending on t. begonia color) and some long, flowing dichondra. Everything flourished in the morning sun/afternoon dappled shade.

If I can figure out how to post a photo, I'll do so.