I can't second the MSF course enough. It's a lot to take in while you're there, but the riding portion takes you through the "best practices" of riding. Practice, practice, practice. Go slow, don't bite off more than you can chew, and the lessons you learn from the MSF course will be invaluable to you. As a side benefit, in many states your MSF graduation is not only your learner's permit, but also affords you a discount on your insurance.
As to bikes, it's hard to recommend a beginner bike without some more info. Do you like to cruise or carve corners? Looking exclusively for MPG? Try many different bikes on for size - Honda Rebels, Ninja 250s, Buell Blasts, V-star 600s, etc. and see what fits you both physically and for the type of riding you want to do. A lot of safe riding depends on how comfortable and confident your bike makes you feel. My Sportster Nightster is a perfect fit for me, but no two riders are alike.
'67 Mustang - out of commission after an accident
'00 Echo - DD
'11 Kia Rio - Wife's DD
'09 Harley Nightster - 48mpg and 1/4 miles in the 12's
I'm 6' 200lb so I can relate to your size. I did own a Ninja 250 for 2 years or so and put 5k miles on it in that time. My knees were cramped on that bike but my butt/back/shoulders were comfortable.
Honestly it had plenty of power, especially for commuting. Mine was all stock and would reach 100mph on the highway, cruise at 70mph at ease (although a bit buzzy), insurance is super cheap, maintenance is easy, carbs are simple and easy to access, and I even rode 2 up on it on a long Sunday ride with a 130 lb passenger... the front end was light but it wasn't terribly unsafe.
As a beginner bike, whether it fits or not, for the price you CANNOT go wrong with a Ninja 250.
I sold mine intending to buy a dual sport (because I can't find comfort on my cruiser for long rides as I enjoy 5-6 hours at a time) but I miss it and wish I'd kept it!!
The Buell Blast or Ninja 500 may offer more leg room but I wouldn't go any bigger than that if you're already concerned about safety. Bigger bikes require more skill, more attention, and more fuel.
+1 on the 250 size bikes. I'm selling my 1000 because it's like driving a hot 454 Camaro around when I'd rather have a Lotus. Small bikes are more fun than big ones. They handle so easy and precise, and though not fast, they feel like they are.
Many people with large bikes eventually return to buy a small bike becase the fun factor is so high - and they are relatively cheap. Often it is a second bike. Having been there, if you don't need the big bike, don't get one in the first place.
Chinese bikes: They can be good - if you don't mind learning about and working on them yourself, which I'd recommend no matter what you buy. Initial set-up and good care are critical as there is no dealer to do this for you like the Japanese bikes. I do all my own work and trust myself more than I do some underpaid kid mechanic anyway. Do research on the Chinese bike forums to see what suits you best. All bikes have problems. Remember that Japanese bikes are not without fault iether, the new CBR250R has a rocker arm issue.