Do Mormons believe in Evolution?

No.

Another answer:

Yes. Mormons believe that God makes Himself subject to natural law, operates by science, and that there is no conflict between science and religion.

Mormons also believe that we existed as spirit sons and daughters of God long before the world was created, and that the method by which our mortal bodies were created is nearly irrelevent. What is relevent is our ability to live by faith, and adhere to God's commandments while inhabiting these mortal tablernacles.

Evolutionary biology as understood by contemporary science is taught in biology courses at Brigham Young University. A symbolic view of the Genesis accounts of creation is easy to reconcile with Godly scientific truth.