The fact that it's not within the grounds of the park makes me think they're not using Six Flags security and those rules won't apply. Could be wrong, but I get the feeling.
Well, this is what it says on the S&S info/Q&A page:
WILL THERE BE SECURITY?
Yes. Festival security is being provided by Griffin's Security LLC. Want to connect with Griffin's Security prior to Skate and Surf Festival? Contact them on Facebook or Twitter (@GriffinsSec). Six Flags Theme Park Security will also be on site, along with EMS services.
So I'm not sure in what capacity the Six Flags security will be there, but it looks like they are not the main security.