I would use SSH and SFTP. But, may I make another suggestion:
If there is any possibility of more than one person wanting to work on the same file, then you should consider a Revision Control System rather than simple FTP. This way you can avoid the possibility of conflicts between multiple updates to the same file.
A widely used system, and my favourite, is Subversion
. There a free book available
that will explain how to install, configure and use Subversion. It's an O'Reilly title, so the provenance is good.