well, they must have had permissions from san Francisco municipal government. where i live i could not even change the tree in front of my house without permission from hoa.
west coast tends to be more liberal but there must have laws like that but enforced by the municipal government, unless the golden bridge is federal property.
btw, there are a lot of chinese in san francisco. visited once (conference) and was impressed by the food there. i had my first time of dim sum experience there. most of chinese restaurants around here are for americans. well, better than nothing...
funding is an issue. those activities must be well funded. it would cost a lot of money to hang those banners, let lone the cost of making those banners. not anyone could be qualified (licensed) for this type of work.
some of those anti-china activists seem to follow the torch relay around; they showed up in quite a few videos (youtube) in different locations. some of them were obviously hired street bums...