Wow....go to a motorcycle forum and ask about this, tires or oil and you have the top 3 most debated MC threads ever.
Some say a 600cc bike is too much for a new rider. Not really. It's all about self control. That, and most places don't really sell "sport bikes" under 600cc and you don't have a "learner's bike" you can easily find in the marketplace.
Other than the Kawasaki Ninja offering a 250cc version, nobody else has an option.
Best ways to learn? Well, most every state has a MSF program, but those teach only the most rudimentary skills. The basic MSF course will usually end with you getting your M/C endorsemant as the final test is everything you need to do to pass the riding test. The advanced is a dubious value as far as how much you will learn, but if it's available, it's worth it. If you've been riding for a year or more, there's little the advanced MSF course is likely to teach you that you haven't learned already from riding.
Frankly, find seasoned sport bike riders in your area (not squids who do little more than stunt and pose), and learn from them. I could teach you more in 30 minutes than you'd learn from experience in 2 years. Sport bikes handle differently from traditional motorcycles, so stuff they'd teach you in MSF doesn't 100% translate...just as stuff you'd do on a sport bike does not translate 100% to other motorcycles. The key thing you need to learn is how to effectively take corners and stop the bike without locking the wheels. ABS is only on the most expensive bikes, and even then you still need to know how to use it properly.
Survival on 2 wheels is all about anticipating the stupidity of everyone else around you and riding accordingly. You need all the gear, all the time. Sooner or later, you will crash your bike....doesn't have to be bad. It's not the get off at 120 that hurts....it's what you wind up sliding into or get run over by. I've had a couple crashes....nothing serious. Nothing more than bumps and bruises (thanks to gear). Never thought of giving up riding because of it. However, there's always that rider you know of you has a get off and dies from their injuries. We love the freedom of riding and we accept the inherent risk it brings.
I laugh when I see motorcycle fatalities plastered in the media. So far, 9 out of 10 motorcycle fatalities covered in the media involves the stupidity of the rider (going way too fast, reckless driving, not wearing safety gear...died because of injuries, not crash). When they talk of motorcycle fatalities, you need to ask for specifics. I don't see a large number of motorcycle fatalities involving riders wearing full safety gear....regardless of riding habits. Responsible riders are most often taken out by some other careless driver not watching where they are going.