Don't get too caught up in the cc thing. Some may tell you not to get a bike over a certain size, but it is not as simple as that. For instance an 85cc 2 stroke motocross bike is going to be faster than a CRF230F trail bike. The main thing for a beginner like yourself is to stay away from 2 stroke race bikes. At 5'7" there are many bikes you could ride. As far as new bikes go the CRF230F is a good option, the CRF150F is a little shorter but there is not a huge difference in power and you could handle either with no problem. The TT-R230 or 125 would work as well as the Kawasaki KLX140. If you could find a good deal on a used XR200 that would be an inexpensive option. Just stay away from 125 2 strokes for now no matter what you choose.
