I live near there. You'll love it - it's a fabulous place and the people are really friendly. Not much English spoken, though, so take a phrase book!
Try Veloce for renting. I've never used them (since I have my own bikes there!) but some guests we had did and found them very good. I'm new, so not allowed to post links, but just Google Veloce Le Marche and you should find it. They have a Facebook page, too.
There are local bike shops around, of course, but I'm not sure if they rent, and sadly I'm not in Italy at the moment so can't check for you.
Enjoy your break!
Oh! I've just noticed this thread is an old one. I can't delete my message, though. Oh well, maybe the info will help someone else. Sorry!
