Figured it out. In order to get sub-basins into the cart I need to "Download" each one separately. That way I get a choice of data type, and they show up in the shopping cart.
Anybody have any idea how long I should expect to wait for shapefiles. The GDB files the site offers are 9.x, too early to load in GM.
I'm getting shape files in about an hour, if I select and try to download 1 sub-basin at a time. Multiple sub-basins send the initial email, but don't generate product.