The cross is a symbol of the crucifixion of the Jesus Christ. We do believe that he was crucified and paid the price for our sins, but our message to the world is that He lives! The gospel "good news" is that He OVERCAME sin in the Garden and death on the cross. Our chapels have steeples pointing toward heaven as a sign of the Living Christ.  
 
Personally, I recognize that the cross is a way that many people are able to think of Him, and that is good. But when I think of Him, it is more helpful for me to think of Him as the resurrected, triumphant, perfect Savior.

because we do not focus on his death/murder/martyrdum. we focus on the good things he did in life (and dying for our sins was good nonetheless) but its not exactly a happy thing.

The Church of Jesus Christ of Latter-day Saints does not use graven images like the Cross in our worship because it is in blatant violation of the Second Commandment given by God to Moses after he delivered them from Egypt.  
 
Some members do wear crosses (especially converts from other Christian denominations) and the Church does not ban the wearing of a cross. It does prohibit the use of a cross on a meetinghouse or during worship as well as any other graven image.  
 
Thank you for the question Brittaney! 
 
I hope my answer helps you understand our practices better!