Last week when I was down there I started to make arrangements to go, and someone told me that they dont let people climb the pyramids any longer. I was told that the Guatemalan govt did some military training there, running the soldiers up and down the steps, and other exercises on the structures. I was told this caused allot of damage to the steps, and so now visitors are restricted from climbing them until some restoration or repairs are made.
Its all unconfirmed, just repeating what a family told me one evening when the topic came up.
I did visit the Mayan Pyramids in HueHuetenango Guatemala two weeks ago though.