Petunias and geraniums are good for hot, sunny areas and don't require too much water.

There is a kind of petunia that is called "Wave." It spread quite a bit and several colors in a large pot look great! I've done that myself.

There are so many kinds and colors of geraniums that you could have a good variety of them and nothing else. There are some that are bush type and some that are trailing.

Good luck!