im 99% sure the 'banding' is a screen only thing.
but on that PDF i didn't actually notice any banding (viewing in Acrobat 5.0). if i zoomed in by 750% i saw some banding.
once printed on a litho press it will look fine. but i would express your concerns to your printer before you send to print, just to be sure.
use quite a lot of gradients and never have had banding on a finished piece. though i have noticed that when viewing such bits of work that are on my website you can see banding when viewed on a 17" mac powerbook. but on my ancient 21" Formac monitor i don't see ANY banding. go figure...!