I really don't like the guys who plant the fakes. I really enjoy hunting for the big ones, and I think if I find a fake, I'd get really pissed. Scubaroo, they're plaster, and some of them are even painted. I know a couple of people who have found them, and that's why I was initially suspicious when I found mine. As Cbulla said, they're easy to tell once you pick them up and turn them over.
DeepSeaWolf, the vis can range greatly, I've been there when there's all of 4" (yup, inches), and when there's been 20'. If you get there early, the vis tends to be better, usually I get out of the water around 11:30 -12:00, and there's already been a noticable drop in the vis. Typically, there's only 1-2' seas with little surge on the bottom, and I've never seen a very strong current, usually just enough to assist you in covering the area (call it 1/4 knot).
CBulla, Sunday is looking better for me, the sinuses are clearing, and I don't think they'll be a prob for the weekend (still taking sudafed at this point, though).