So, I probably haven't been on a bike in....well a long time. I signed up for a triathlon (it's in 8 weeks) and I need to start training. I'm thinking about purchasing a used cyclocross so that I can use it for the triathlon but not just strictly only on the road afterwards. I'm 5'4" 130lbs. I have NO idea what size bike is right for me, what's a good brand? How much should I spend as a beginner? Is the cyclocross the right bike or should I just purchase a cheapy used road bike to train for the tri and later a beginner mtn bike? What should I be looking for? Thanks in advance if anyone has suggestions.