Marcie -- I'll do my best to answer your questions; others may have more experience in this than I do. Here in Ohio, if you join a center, as long as you stay within the same franchise you can go to any other WW meeting and pay the same price. Our franchise covers the whole NE Ohio area, so it gives you a lot of meetings to choose from. If you join at a center and want to use the online site, you can only access certain portions without signing up and paying a monthly fee. In our franchise the cost for the online site is something like $12.95/mo. We give our members an access code that they can use to get on the site FREE, one time, to check it out before they subscribe. And I think what we've been told is that if someone comes into our meeting who's normally an on-line member they can attend the meeting, but we have to charge them a regular meeting fee ($12). We waive their registration fee.
I hope this helps! Good luck -- I see that you've done quite well so far and I know you can make your b-day goal!