If you get a chance, go ahead and attend. As was stated, it doesn't cost plus the results are available to all the teams. From the ones that I have witnessed, most of the younger attendees appear to enjoy the tryout.
Just be sure you are in shape and ready to play when you go out there as most of the other attendees will be and at many of the camps, they limit the number of position players they let swing the bat - only letting players that looked good running or fielding or players they had a prior interest in or have a certain physical makeup hit.