could be several different things--hibiscus, mandevilla or many other suggestions but try putting up a picture to the "ID this plant" forum. You definately will get it ID'd there. I have had tons of luck there.
Teresa

Sounds more like Ruellia to me. It gets canes about 4 ft. tall. Mine has purple petunia like flowers that open each evening and drop the following afternoon. Mine overwintered in the ground here in zone 7 but has yet to bloom this year. I plan to take it when I move and will try a sunnier location next year, maybe with a bloom booster fertilizer. Plant delights nursery has pictures in their plant catalog. Look at the tall purple form.

Here is a link that might be useful: Plant Delights - Ruellia Bottom of Page