wow, sorry i missed your question back, you must have find the answer since.
when nuke starts it looks into few default path like .nuke so any file there should be read and you would just need the command to call it in your menu.py
for a specific folder you add the path into init.py (still in .nuke)
something like :
nuke.pluginAppendPath( "/usr/people/oliv/.nuke/PythonScripts/" )
i am not sure it was the answer to your question, some more smarter people than me can give you more help on the foundry python mailling list nuke-python@support.thefoundry.co.uk you can register free on the foundry website.
sorry for the late answer
O