I'm not keen on joining gyms. I've had two ex-significant others who've joined and then pay the monthly fee while rarely going. They often can't get out of the year or two or three obligation they signed up for, so it turns out a real waste of money.

I say go a few months paying at the door. If you keep it up and are totally sure you're going to keep doing it for at least the minimum contract period, then go ahead and join.