At your height you can get on just about anything. You might have to have it lowered, but not by a whole lot. And getting one lowered is no big deal.
For a first sport bike, you might be better off with a 600. Just because they're lighter - you won't lack anything in the speed department, trust me.
They aren't harder to ride - they're much easier in fact. The problem is that because they respond so intuitively, you may give it signals you aren't aware of.
With any bike, and with a sport bike in particular, it's always a good idea to ride it around an empty parking lot for as long as necessary to get a feel for it.
I've been riding for 11 years now and just got my first sport bike 3 years ago. Even with my experience, I rode it for the first time in a parking lot - my husband took it there for me. We both agreed it was a good idea. And it was. Because just sitting on one doesn't give you any idea of what it really feels like to ride. When I took off, it felt sooooo weird....now it feels completely natural.
You could certainly start with something larger, but I think a lighter bike makes you feel more confident.
FWIW, I have the 04 ZX6R 636.
Oh yes - I've heard that dirt is the very best experience you can have. But it wouldn't be a bad idea to hone your skills in the MSF course.
And please don't be discouraged by all the negativity. If you want a sport bike, get one! If you were a complete newbie I might agree it's best to start on a cruiser. But you're the best judge of your skill level and of what you will be happy with.
I kept my Magna after getting the 6, because I figured if it didn't work out I'd still have something to fall back on. It's true it took me a while to get used to it, but now I'm selling the Magna because it BORES THE CRAP OUT OF ME. I took it for a ride once, and I seriously was so bored on the way home I felt like calling a cab. And it handled like a camel in comparison.
And yes, I'm sure you realize that sport bikes aren't as comfy as street. But we're not all decrepit old geezers. (Well I am, but whatever). I decided that I'd rather have short FUN rides than long boring ones. And my hubby has had sport bikes since 76 or so, and we've taken longer rides. So what if you have to stop now and then?
lol - ok, rant over.