Mayer – who donned a t-shirt featuring lyrics to second single “Queen of California” once he spotted it for sale inside – mingled with friends, family and industry pals before settling down in the back corner with a pile of Sharpies, ready to meet the crowd gathered outside.
Accepting letters and music, a mellow Mayer, 34, gave his full attention to each person who approached the table over the course of two hours.
“He looked like he was having a great time interacting with fans,” an onlooker tells PEOPLE. “Especially since he won’t be able to tour.”
– Sarah Michaud and Sara Hammel