The Hexagon IS visible, and is increasingly so as the angle of Saturn's tilt to Earth increases. As Brent mentioned though, it will be very foreshortened. BUT, to see it you need all your ducks to line up in a major way: perfect atmospheric conditions, good optics, a keen eye and a big dose of patience. Filters may help too as it is not a stand out feature. I think the technical term for seeing it is "suck your eyeballs out of your head difficult"...
There are many Earth based photos of the Hexagon, including from here in Oz as Saturn is perfectly positioned for us. Photos are also enhanced to bring out the Hexagon:
http://www.popastro.com/planetary/ne....php?id_nw=181