First off, it’s helpful to define what is meant by the term “evolution”. If, by “evolution”, we’re talking about the process of natural selection by which species change due to certain members having advantageous traits, then yes, I think it’s safe to say most, if not all, Mormons believe in evolution. However, if evolution means do we believe that human beings descended from apes then no, Mormons generally don’t believe in that kind of evolution (although I know there are some out there who do).
There’s also the question of whether those Mormons who believe in natural selection believe that all existing species descended from green algae vs. being placed on earth in some other way by God. My guess would be that 99% of Mormons haven’t thought about it since it doesn’t affect our theology one way or the other.
In fact, whether or not Adam and Eve were descendants of apes or green algae doesn’t really affect our theology either. I do believe Adam and Eve existed and that all humans are their descendants, and I don’t believe Adam and Eve were descendants of apes or cavemen or anything like that, but if they were, so what? It doesn’t change anything for me so I don’t care. It’s interesting to think about the various possibilities, and I’m curious to know exactly how it all came about, but whether it’s one or the other doesn’t make that much of a difference to me.