Try the main reservations number at 800-352-0714. That's who I've called before to check loads. You can list through them too. They've always told me the loads, but I let them know I'm a company pilot. I think they'd have no problem giving that info to an offline jumpseater though.

You could list through them, but most people just show up at the gate. I'm not sure what the official policy is, but everyone's so laid back around here that they won't care either way.