As a personal trainer, that used to work at the Bally's in South Philly, I can tell you they will do anything to sell you a membership and personal training.
If you are serious, sign up. If you are serious, be ready for a 3 year commitment, because that's how long most of the contracts are for. Read the tiny fine print, because the interest rate on even the short term memberships, can range up to 22%.
Honestly, there are probably more cons than pros for signing up at Bally's. The pros however, are that there seems to be a Bally's just about everywhere, and the monthly payment can be really low. And some people, really need to hit the gym to change their lives.
I would like to see some more details before the fine print but every time I try to view any section of the site it asks to register. Personally, I'd rather not give out my info before I know what Im getting into.
This may just be me and my browser settings though.