How to install a 2'x3' metal sign in beach sand

[dwdanby]

I plan on 2'Wx3'H one-side-printed metal signs, they will go in sand but at the edge of where the dune grasses begin. It's much harder ground but still basically deep sand. Well, the whole town is. I want to ask about what upright I need to get (the sign will be bolted to it), and then about how deep to dig and what the dimensions of the concrete base should be. And any other advice is sure welcome. I'm drawing up a proposal and need to find all the details I can. Thanks all!