There are too many answers to your question. There are many plants that will work. It all depends what shape and colors you want. Geraniums always perform well from spring til fall with a few filler plants. There are many colors and also come in ivy as well.

I'm in z5 NY so our plant availability shouldn't be too much different. If it's full sun, or gets a good deal of sun, maybe petunias or lantana would work for you. For part sun to shady, I like impatiens for constant color.

Originally on my way to the nursery I did have petunias in mind. However after talking to a few people there they directed me to what I eventually bought were Ivy Geraniums they told me they preform well in heat although I am only in RI and bloom most all season