My vote is for the
Suzuki SV650.
It's a mid sized bike, so you won't have a toy that you'll grow out of as soon as you complete your motorcycle training course. It looks great IMO. It's very light and nimble. The V-twin has good torque and it's pretty smooth for a twin. It will cruise comfortably at 65 mph. Comfortable riding position (as good as you're going to get for a non-cruiser/non-touring bike, i.e., heavy and clumsy). It looks like a Ducati Monster without the exotic price tag. It's just a great bang for the buck bike and it's such a versatile bike. It's sort of a modern Suzuki GS500 or 550, if you will.
The base price for a new one is very reasonable, but you can look for a clean used one in your price range.
Larger photo.
If you want a bigger and great all around bike, go for a Suzuki Bandit 1200 or even the 600. They are great UJM's (Universal Japanese Motorcycles or what I typically call them.. Standards because they are standard, do-it-all motorcycles). You can get great deals on either of these bikes used and they are bulletproof. The B-12 might be a little too big for you though.
Heh.. You may think that I'm a huge Suzuki fan too. I'm actually a Yamaha man myself, but I think that the Suzi SV650 is a great bike for you.
I'll have to agree with some that motorcycles are dangerous. Even if you're the best rider in the world, you are riding around the streets with a bunch of knuckleheads! You really have to watch those Aholes out there not paying attention driving their cages while jabbing away on their cell phones.
Sal