My understanding of the settlement of Nevada:
Everything I've ever seen indicates that outside of the Mormon settlements in the greater Salt Lake area, Utah and Nevada were pretty much entirely empty of settlers whose opinion would have been counted (i.e., Anglo-Saxon whites). Keep in mind that when we talk about "Utah" establishing independence any time before the 1861, we're referring to the Utah Territory, which included all of modern-day Utah and Nevada. The first significant settlement in Nevada was established in 1849 and named, tellingly enough, Mormon Station (now Genoa).
The Mormons certainly considered Nevada just as integral a part of Deseret as they did Utah, and even the US government (whose attitude toward Mormonism could at best be described as cordial dislike) accepted this when it established the bounds of the Utah Territory in 1850. Salt Lake would have liked to be able to claim the New Mexico Territory, too, but unlike Nevada, it was already a little too thickly settled for them to do that convincingly (which is why giving Deseret cores in New Mexico and Arizona is a good idea, IMHO).
White, non-Mormon settlement in the western Utah Territory didn't become a significant phenomenon until the discovery of the Comstock Lode in 1859, and by 1861 the region had enough non-Mormons to establish itself as the Nevada Territory. (The preceding, btw, was all drawn from the 2003 edition of the Encyclopaedia Britannica.) Even then, settlement was confined to two towns right on the California border, Virginia City and Fort Carson. IMHO, the province of Fort Carson is still too large to give to California in representation of this, but if you're talking about Californian/Deseret independence at the time of the ACW or later, I think it's something that can be justified. Prior to 1860, however, IMHO Nevada should definitely be just as integral a part of Deseret as Utah.
Ian
EDIT: Noticed while playing: the "province of Fort Carson" to which I refer in the last paragraph is actually the province of Carson City; I would assume Carson City and Fort Carson are one and the same geographically.