Depending on your size the 250 ninja and Blast (with european Rotax motor last time I looked, not very "american" but maybe someone else makes them now) might be a little slow, they (the 250 at least) are still far from slow, but you might be better served with the 500 ninja or something else that you will not outgrow as quickly. That 250 is a badass handling little bike, but buzzy and a little slower accelerating than standard size bikes, but if you are really interested in bikes it will teach you to shift properly to keep the bike in the rev band, and it corners like nutz, I've always thought about getting one as a play bike. Heck 30-40 years ago bikes the same power (though different torgue curves i.e. less buzzy)were full size bikes that people tool cross country.
I think a standard with no body work is a better choice as you will probably drop it at least at low speed, have it fall off the kick stand etc and that body work gets scuffed up and unattractive quickly and is expensive to replace. The GS series bikes mentioned above are good choices as are the Yamaha seca and just about any japanese 500-650 without a lot of boy racer body work.
Skip Harleys starting out, except for the sportsters they mostly have a cruiser slouchy riding position, which although it gives false confidence to new riders and women because you can easily get your feet on the ground, it is poorly suited to long rides and good control of the bike. Also, most importantly, you are paying a high premium for the name on the side as the engineering and build quality, depending on the age of the Harley, are at best equal to japanese bikes. If all your buddies have one you'll want one, but start out on a mid size japanese bike first to see if you like the sport.
Take the MSF like they said, get a full face helmet that has plysterene (hard stuff not soft stuff) in front of your face and at a minimum get a good MOTORCYCLE jacket (i.e. a Vanson etc made out of thick leather v. the fashion leather motorcycle jackets places like the mall leather stores carry) boots, helmet and good gloves.
I don't seem to have the time to ride anymore,but I rode a lot for about 15 years, it was some of the most fun I have had. You see and smell so much more of the world from a bike.