Dan, riding a dirt bike or dual sport will teach you more about motorcycle control in six months than you could learn in ten years on the street. and at a safe velocity. It is ANYTHING but a waste of time.
There are two basics to safe riding one is motorcycle control, the other is street smarts , strategy if you will-
The bike forums out there contain some great info and some VERY knowledgeable people IF you go to the right one- the sportbike forums tend to be filled with a bunch of squids. Try the ZRXOA or Adventure rider forums, these folks are by and large very experienced motorcyclists and actually have opinions worth listening to. Go there and ask about starter bikes, you will get a lot of good responses.
Anothe great resourse is motorcycle consumer news, online and in print.
My advice - buy a used dualsport like a suzuki dr400, or a kaw klr 650, or if you have short legs a klr 250- buy some gear and ride the hell out of it. Feel whats it's like to slide the rear under power and with the brakes. Lock up the front tire and feel it wash out. Jump it a bit . Spin some brodies. After a year go buy a street only bike and amaze your friends! I cannot count the people i see riding big expensive bikes who cannot ride worth a damn- you see them duckwalking around slow corners, weaving and jittering all over. Remember, it is not BIKE, it's the RIDER.
Stay safe and have fun, man.