Ask YC: How to setup a virtual office in the Bay Area?

We are an Aussie startup and are looking to setup a basic presence in San Francisco/Bay Area.

Basically we just need a legimitate looking address for the website and for mail, aswell as a SF (415) phone number that can either be redirected to Australia or a low cost answering service.

We are on a tight budget as you can imagine.

Can anyone recommend a Mailing Service or Virtual Office service that was cheap, easy to use internationally and quick to setup?

Any advice?

Thanks!