We believe salvation is independent of denomination, which very few people realize is a tenet of Mormonism. In fact, given our belief in the universal potential of the Atonement of Christ, we believe it is independent of religious affiliation in totality - IF someone truly did not have a chance to accept Jesus as Lord and Savior in mortality. We believe those judgments will be made by our Eternal Judge, Jesus, the Christ - not by we who see through a glass, darkly. Allowing for salvation outside our own limited understanding is an aspect of humility and gratitude that is central to our theology. (Since there is not one of us that "deserves" salvation, we need to avoid the natural tendency to say that others "don't deserve it". We are commanded to love ALL and not judge ANY - in that regard, at least.)
Ironically, we get told all the time that we believe only Mormons will be saved, while our actual theology allows for the salvation of MANY more of God's children than the majority of Christian denominations allow. We leave salvation open to the reaches of grace beyond the opportunities of this life, while many other Christian theologies deny salvation to all but those blessed to hear of Jesus and the Gospel and accept them in this life. Thus, the number of those who have a shot at salvation within Mormonism's view is exponentially higher than that within almost any other segment of Christianity. It really is one of the misconceptions that bothers me the most, since it is a HUGE moat and beam issue, in my mind.
As succinctly as I can put it, we believe the Bible on this one. We accept Paul's statement in I Corin. 15:22 that "as in Adam ALL die, so in Christ shall ALL be made alive." ALL of God's children are saved from physical death and will be resurrected. ALL will be saved from the effects of the Fall - from those things that are out of their control as a result of being born into a sinful world. ALL will have the opportunity (somehow, at some time) to hear the Gospel of Christ and accept it or reject it. We don't know many details of how that will happen, but we extrapolate from the words of Paul and Peter that it will happen either in this life or in the post-mortal life (whatever title we might give it).