I took a big Google walk around Crissy Field. There is really no CCTV on those buildings along Mason Street or Marine Drive. Various lighting on the buildings, but no CCTV that I could see. (Google image Nov 2013, things could have changed a bit.)
From my observation, Crissy Field is a popular place for walkers/joggers (a big group of picnic-ers too) and while it has spectacular views of the bridge, it is still quite a way away from getting up onto the bridge if a person is on foot.
I did notice several emergency call phone boxes, solar powered, along the foreshore walkway.
There are a couple of seemingly popular little piers along Crissy Field. Possible Syd was seen by an early morning fisherperson? During the daytime there are quite a few people fishing.
It doesn't seem probable that Syd had moved out of dorms and taken up residency in the adjacent marina district there. Possible, but the housing there looks quite expensive. So, as others have mentioned, it would seem that Syd had some other mode of transport to get there.
خرائط Google