The short answer is, yes, you do have to be a member. However, that was as of a couple of years ago. There is a school which operates it's PE classes in the gym (not sure if both sides or not) then in the evenings there is almost always a league or two that practices on both sides of the gym.
I don't know but if they are open, just pop in and ask someone!
Thanks! Your answer is awaiting moderation.