Car show and Swap Meet

I'll be there, early if I can. help me out here guys, lets say I have some stuff to swap, can I wander around till I find someone that has what I want and then barter with what's in the trunk, or do I have to buy a swap spot and hope I don't miss a good opportunity while I'm out looking at other stuff? A swap space is cheap so I'm not concerned with that i just don't want to haul it all out. tell me if I'm being stupid.