Since I'm just having protected posts for workshops and people have to pay per workshop, I don't think this will be an issue for me. No one will sign up JUST for the free member level. They'll go to a workshop page, see they have to pay for it, and get signed up for the free member level the same time they pay for the workshop.
But, from here:
with only a free level, if the person clicks on "select", it takes them to the checkout page to register, but there is also the payment info box underneath it.