Find your niche . . .
I'll tell you what I think . . .

. . . I think Americans
know they have lots of food choices. And, if we are just talking volume - yep, they do. They don't need to sit behind the wheel of their car for long before arriving somewhere they can find food.
Kate, if the market you are attending is too much of a flea market, customers aren't arriving with the idea of food shopping in mind. You may want to do a little
shopping yourself, for a market that's more food-centered.
Now, the customers as this food-centered market may not be showing up hungry either. I bet 90% are arriving with the idea that "this will be fun." And, that's real positive

. There's a happy feeling to seeing people drive into a parking lot with smiles on their faces . . .
Entertainment. Entertain them with something different. Yes, "grandma's vegetables" can be entertaining. After all, some people never cook . . . I'm talking adults here. Yes, even parents :/.
You may have "grandma's vegetables" and maybe you should go whole-hog in that direction. Do your darnedest to look and act like someone's idea of what a traditional grandmother looks and acts like.
Now, I don't think of you as a grandma-type and I do think it is great that we have a Heidi on TEG who has goats and makes cheese

. Marginal entrepreneur that I am, I'd have her doing demo's at a farmers' market . . . dressed like she has just stepped off a box of cocoa:
http://www.amazon.com/Roma-Swiss-Miss-Costume/dp/B001D9X8OW
Now, I'm sure that you could go too far in all of this but remember: "entertainment." And part of the customer's entertainment is that they make a purchase. You want them to make that purchase, not just stand there and smile. And the product can't be too exotic because you want them to use it when they get home and come back for more. There can be only so much time spent in
educating the public as to what grandma or a Swiss Miss would do with those products. I mean, you aren't necessarily just there for "public service."
Signs are important! Products that are different than the ordinary are too

.
Steve,
rambling a bit