You should defiently take the MSF course before you buy a bike it will prevent you from making alot of stupid mistakes and you will also get your license.

From reading your post I suggest something like a suzuki SV650. They are a great bike to learn on, handle great, good amount of torque, inexpensive, and most importantly wont kill you. My friend got a 2001 new out the door for like $5000, used they are muuuch less.

Now let me tell you, your friends are idiots for getting liter bikes for their first bike. Yeah they might look badass and be faster, but you will learn to ride %100 better than they will on a small bike, you will live, you save money, and to tell you the truth after a few months of learning on a 600 you could keep up with them everwhere but the highway.

Ninja's are fine bikes (its all preferance), they do tend to have a softer rear shock (no big deal your not a AMA racer its your first bike). And all the superbikes/sportbikes have adjustable suspension stock.