I would suggest that you go to a few bike shops and sit on some bikes. Since you do not have a lot of experience, you should stick to a 600cc at the most. You may want to avoid the super sport bikes, until you gain more experience.
I think it's a comfort level. If you are comfortable on your toes every time your stop, go for it, but I think you are opening yourself to risk do to the unlevel roads. Plus a motocycle is least stable at a stopping point, You can better insure its stability by having both feet firmly planted...
You can wear it, but it's not going to protect you if you hit the ground. Dirt bike apparel is designed for the dirt, and street gear is designed for the street. If you plan on getting on the freeway with a 250, you definitely need more protection than dirt bike gear provides.
Hopefully...
Mad Jack gives good info, but I disagree with his suggestion that short people should not ride sport bikes. I'm also 5'2" and I have a GSX-R 600 and my feet are firmly on the ground. The newer ones 2006-2009 have a narrower tank than it's predecessors, which make it easier to straddle the...
After you take the MSF rider's course check out a Suzuki Boulevard s40. It has a low seat and it is very comfortable to ride, especially for petite women. It has a lot of get up and go, so you won't out grow it quickly. It was my first bike and it is a lot of fun to ride...
I strongly suggest taking a MSFsafety course before you purchase a bike. You will learn much more than you would on your own or from someone else. Look into a Ninja 500 or a Suzuki GS500F. Both are sports bikes but would have a little more power so you won't get bored too easily.