U-turns are legal in Georgia, as long as the road is straight and there's no sign. There's no requirement on how wide the median must be.
I'm pretty sure that if an officer saw you make your "U-turn-on-red" that he'd pull you over and cite you for running the red light. I don't see how the statute can be applied to permit you to make a "turn in the opposite direction," but I haven't pulled the case law.
There's a handy free online version of the Georgia Code at
http://www.lexis-nexis.com/hottopics/gacode/default.asp
From the Official Code of Georgia:
§ 40-6-121. U-turns
No vehicle shall be turned so as to proceed in the opposite direction:
(1) Upon any curve;
(2) Upon the approach to or near the crest of a grade where such vehicle cannot be seen by the driver of another vehicle approaching from either direction;
(3) Where such turn cannot be made in safety and without interfering with other traffic; or
(4) Where a prohibition is posted.
§ 40-6-21 (a)(3)(D) Left Turn on Red
Traffic, except pedestrians, facing a steady CIRCULAR RED signal, after stopping as provided in subparagraph (A) of this paragraph, may make a left turn from the left-hand lane of a one-way street onto a one-way street on which the traffic moves toward the driver's left but shall stop and remain stopped for pedestrians and yield the right of way to other traffic proceeding as directed by the signal at such intersection. Such vehicular traffic shall not make a left turn against a steady CIRCULAR RED signal at any intersection where a sign is erected prohibiting such left turn;