I can find information on the cost and routes, but not how OFTEN they run. Does anyone know? Thanks!
I believe it's ~ every 10 minutes..see link below (may need to translate if you don't know Italian)
http://www.anm.it/index.php?option=com_content&task=view&id=1299&Itemid=258
Scroll to the bottom for a description of each (also confirms that they run every 10 minutes)
http://www.freetournaples.com/transport-in-naples/
Basically, the go up and down with a brief stop at each terminal, so 10 minutes or so sounds reasonable for most of them.
Thank you!