Sure! You can use the same username/password for the listings & ratings section, and the classifieds section, as with the message boards. Just click the "post listing" link from any page from the listings & ratings section (
http://gymchat.com/listings) and fill in the form. Then you can add your review by clicking the "Add your Review" link from the page of the listing you posted (scroll down that page).
The good thing if your club signs up and post their club listing themselves is that then they would have access to reply to reviews made for their club. But in that case, if your club is interested after you have already posted the listing, we can just transfer the administrator access for their club listing to their username, so don't worry!