Well, I'm fairly certain this isn't a Zin, just based on the leaf shape and cluster alone. I'd be over the moon if it were. Though it is a prominent grape in this region, you guys aren't off the mark about that. I had the pleasure of tasting a Zin from a vine aged 107 years recently (Ironstone Vineyards, for those interested), and was surprised at how much sweeter it was than the younger 85 year old vine wines.
Anyway, I gave my grapes a taste (which was rough, mind you, since I don't actually like grapes) and was distinctly reminded of the table grapes that my kids eat. Very sweet, very Concord. Welch's grape juice, even. Huge seeds, blech. Didn't detect any muskiness (foxy?), but then again my palate is probably poor or just leaning toward the sweeter flavors. I always pick up oak, leather, berries, and sort of a whiskey sweetness first when diving into a red wine.
Either case, I'm still leaning toward an American variety (Vitis), transplanted most likely. The guy offered to let me pick his whole yard, but I'm worried that once I go to all this trouble then the "foxy" taste will punch me in the face and I'll hate it. I should really get my paws on some actual vinifera and learn the difference.