Hundreds of Neshamas,
Would you consider writing an anonymous open letter to
http://www.theyeshivaworld.com/ ? I bet that would get the attention of your Yeshiva administration and many other Yeshivos too. You don't need to mention your Yeshiva's name, nor do I think you should. Let every Yeshiva think it's them and take precautions.
These are problems that need to be addressed, both by having the neighbors block their wifi and having the Yeshiva use their influence (with whatever method they find effective) to stop the Bochurim from accessing the wifi through their devices.
While you're writing the letter maybe you can slip GYE into the message too
YVY