You have nothing to be nervous about. BYU is basically supposed to lose that game, so, in a way they really have nothing to lose. If they play tough (which with Bronco's coaching style they will do no matter what) and lose, oh well, at least they didn't lay an egg against UNLV. If they win great. BYU has every chance of winning that game.
UCLA on the other hand has everything to lose. If they lose to BYU they'll be perceived as awful.
Arizona is the game to be nervous about. If BYU is "back" and wants to reestablish themselves as more than just another MTN west team they have to beat teams like arizona that have been bad the last few years. PK says it almost every day, there is no excuse for loosing to Arizona, just freakin win baby.