I think marketing skills are incredibly in demand in an early stage startup, even more so than technical skills! Look at this recent HN post and what people would want to read about most: http://news.ycombinator.com/item?id=2012959
If you're a nontechnical person joining a startup, don't bother learning to hack beyond a very basic understanding. You won't be any good at it for a while, and they probably already have smart technical founders who will tackle the difficult technical problems.
There are lots of brilliant hackers in the Bay Area. People who know marketing seem to be far more rare here, and as a result are highly sought after by the smart startups that have a real business model and understand they need marketing to succeed.
If you're actually good at copywriting and can drive serious traffic, you will have numerous startups literally BEGGING you to to take their money and run ad campaigns for them.
It's important to make a distinction here. If you come from a brand advertising background, then forget it, no startup will want to hire you.
If you know performance marketing, and can deliver conversions and predictable ROI, you can rapidly and easily get as many consulting clients(which lead to job offers, if you want) as you can possibly handle.
Go to startup meetups, mention that you know how to drive traffic and convert it, and before long you'll have a stampede of eager startup founders beating their way to your door.