Pressure wash a new cedar deck?

Hi,
We just had a new cedar deck built and we have been hearing some contradictory statements about how to prep it before staining and finishing. Most of the contractors we have spoken to have said they propose to pressure wash the deck, but we have also seen comments in some forums that pressure washing is not appropriate for cedar because it raises the fiber, drives moisture into the wood, etc.
What is the best approach? I do not have the time or inclination to prep and sand a deck myself, so we would like to hire someone to do the work - but should we trust the folks who say it is no big deal to pressure wash?
Also - it is September now (we live in suburban Chicago) and no doubt the weather will start turning soon; should we let the deck weather over the winter and then prep and finish in the spring/summer?
Thanks
Dan