Mostly we heard, Sunny is better, wet feet is bad. But, it is a BUT, read through fllowing thread, you'll be surprised.

Here is a link that might be useful: Very funny thread about Gardenia

i am growing a gardenia in shade but not deep shade. it is bright, filtered light with no direct sun for any length of time. blooms beautifully and the foliage is better looking than some i have seen growing in full sun.
i think in a hot climate direct sun is not necessary but dense shade is not good for flower production.