I'm just down the highway from Squamish (Paradise Valley). I've heard that the Dead hung out in West Vancouver before or after that show. There's some old timers around that recall that. Vancouver had a very hip scene going back in 60's. There's a local in my community who met the Dead in 66. He was the drummer for the band that went on before the Dead. No one in Vancouver had ever heard of these guys as the Dead did not even have a record out. He told me Janis sat in and did a long rap with Jerry rockin' out.
Paradise Valley would have been a haven for draft dodgers and living off the land types. It's a steep boxed canyon and in those days would have been considered very remote. Logging road access only. Its still considered fairly off the beaten track.
As per a recording. Check with David L at the Vault. He's pretty good at getting back to folks. There are some decent board tapes circulating of the Dead's run at the O'keffe Centre in Toronto in 67 (68?).