In the Manage Scripts dialog, there is a checkbox next to each script and folder. Those with the checkbox are visibile in the Sscripts menu. Deselect the checkbox for the ones you want to hide. The scripts can still be called from buttons and other scripts, just not by selection in the menu.
If you want the scripts to be visible to other users, then you will need to use FileMaker Pro Advanced to create a menu set without the Scripts menu, and assign that menu set when a user logs on with Guest access.
What both Rob and Keywords said with the caveat that "run script with full access" is in effect temporarily elevating the users permissions. I might suggest creating a custom privelege set specifically designed for the "guest" users that allows them only to execute the scripts they are permitted to execute so that the temp elevation is not needed and control of what the guest users can do is regulated in the security settings and not in the scripts settings. Just something to think about.