There are a lot of 250s on the track as well. I had mine up to 98 with no performance mods. The 300 will go faster with performance mods up to 120. Yamaha R25 is also worth looking at. http://www.topspeed.com/motorcycles/motorcycle-reviews/yamaha/2014-yamaha-r25-ar161316.html
I thought I loved the 250 I had but it wasn't, I am in love with my ninja 300! There are tons of ninjette riders your size. Its a great place to start but the 300 is also awesome.
Riding filled a huge whole in my life. I was happy but felt I was missing something, started riding and feel in love with it. i justvhste winter. As a bonus Hellmutt is happier too. I love it, and make better sammiches because I ride.