If you live upwind of the accident, drive away from it. If you live downwind, drive at right angles to the wind. In the inevitable panic, the roads will probably be impassable anyway. Just lock up the windows as airtight as you can until you're able to get on the highway. It may take a day or two before you can travel, but do so as soon as you can. Use the time you have before you leave to inform yourself by radio/tv and prepare your supplies for the evacuation.

The utility of potassium iodide as an antidote for radiation is severely limited. I guess it won't hurt to use it, but there will be plenty of other isotopes around to cause mischief. A full tank of gas and a handgun will be a lot more useful.

You can take some comfort in that the panic will probably cause more casualties than the actual accident, unless the worst-case scenario materializes (full meltdown and containment breach, or terrorist attack on the spent fuel repository).

If Turkey Point blows and the wind is southerly you probably won't be hearing from me again. Alligator Alley is the only way out of town.