Do I still send a thank you letter after a job interview?

I went to a hiring event yesterday where Jack Astor's was hiring for many different positions. I applied for the server position then I met with one of the restuarant's employee's and sat down for an interview. It went pretty well (or I think in my view it did) and I left on good terms. He said that he will push my resume to the manager and he will get in touch with me for a second interview (that is if I get invited to one). My question is do i send some thank you letter? I haven't even met the manager yet and this was the first interview.