It is hit or miss, really. I have sat in the chat room for several days without a single person stopping in to say hello. But, I have also gone in the chat room and, within minutes, had five or ten people show up. It is really just the luck of the draw.
There are no rules against posting in Casual Conversation to let people know you are in the chat. That usually helps get people in there.
Another thing to keep in mind is that the chat statistics are cached, and update a maximum of once every three minutes, and even then only when the forum index page is loaded. So, if you only hang out for a minute or two, and nobody hits the forum index page after you logged in, the chat statistics may have never updated to even show that you are there!
Also, make sure you stop by the scheduled chats. There is usually a pretty good turnout, and they are a heck of a lot of fun.

Mike