There is going to be talk about God at BYU because of the nature of the institution. That said, I don't think anyone LDS would want to be rude or pushy about telling you what they believe. If you ask, you'll probably get an earful but if you don't, you probably won't hear much, if anything. Members who follow the Church's teachings on this issue believe what they believe and should definitely grant you full rein to do exactly the same thing without even the slightest hint of judgment or disapproval.

There's no law that says you have to be LDS, or even religious at all, to be a BYU Cougar Fan. All who cheer for the Blue and White are welcome!