I would try to stick with "native" plants for an area where you will not be around to water. I have a bed with similar conditions to what you describe filled with what I'm pretty sure is southern sheild fern. About the only attention it requires is "thinning out" every few years, as it spreads within its bed very well. I got some as a passalong from a neighbor who has it growing thick in a wide variety of light conditions. I have christmas ferns around which i don't really bother to water either.

As for flowers, I have found some native rudbeckia (like stuff I have dug up on plant digs) to be very tough and willing to bloom without full sun. I like Rudbeckia triloba, which has smaller flowers than other black-eyed susans, but lots of them on plants that get about 3-4 ft high. There are also many shrubs, like native and non native azaleas which don't require much attention. All the many choices make it more fun to decide.

Lantana, lantana, lantana. Start with a "Miss Huff" larger type in the back. Plant one of the medium height yellow ones in front. This will give you the same color as marigolds all summer long. Cut and cover the trunks with buckets of leaves in fall. Remove buckets about April 1. Otherwise, they are pretty much carefree. They thrive on neglect and love dry weather.