Student or Learner
We were playing in Madison Square Garden and it seemed as if people were coming out of their apartments and homes and being prepared to let their guard down for two hours.
--- I understand that this phrase means that people were coming to their show to relax, forget about problems?
Originally the image referred to a boxer - if he 'let his guard down' it was possible for his opponent to land a scoring punch unopposed. But now it just refers to being defensive and expecting to be attacked or taken advantage of in some way.