You'll probably want a road bike of some sort or, at the very least, go for some slick tires on your Cannondale. There's no terrain on the MS 150 that requires a mountain bike, though I've certainly seen folks riding them. It really just depends on what you're comfortable riding. I'd suggest joining up with a team, since the logistical support is very valuable, and start training early. Make sure you do some hill rides because there's not much in Houston to prepare you for the hills of central Texas.