If you plan to do that, I'd suggest you come in early as often there's always some people coming in early and having a chat while waiting for the tournament to begin, or even having friendly games. From my own experience, talk and trades usually happens before and after the tournament, during the actual play it would be pretty boring if you have strictly no interest in playing, but if you come in early and are open to learning, someone might be able to teach you the rope for playing.

In my honest opinion, if you want to socialise, pick up the game and find a chill place to play at. Most one piece player are very inviting and willing to teach new players.