We saw Samual L. Jackson outside Hollywood Studios when we were there last may. He was by himself, wearing a long raincoat, dark glasses and a hat (I guess that he didn't want to be noticed), but he was smiling the biggest smile, just like a little kid. We didn't bother him for a picture, it was his vacation too!
I just wanted to mention, there is an undercover security guard at HS that looks just like Samuel L. Jackson. Everytime we are there for rope drop, we see him there by the front gate. The first time I saw him i thought it was Samuel L Jackson too, but then after seeing him multiple times we realized who he really was.
i am not sure if that is who you saw, but I thought it was coincidental that you had your sitting at that location.