Yep, they will grow. It's fun to try seeds like that see what you get. My daughter dumped a bunch of seeds from a store-bought pumpkin into my veggie bed. She didn't dry them or anything, just dumped them in there. I think every single seed sprouted as there were at least a hundred coming up. They got vines about four feet long before the first frost killed them.
I'm in Atlanta area Last year 2007 I got pumpkin seeds from HomeD store... and I DIDN'T EVEN GET ONE PUMPKIN although they grew nice leaves and had plenty of nice big flowers. I'm afraid it didn't get enough morning sun. I know it got plenty of water despite the drought 'cause I did drip irrigation. Does anyone know a good variety for Atlanta area? Prefer one with mildew resistance. I might have to try buying a grocery store pumpkin and plant it. Oh yes, and when should I plant pumpkins for Halloween? I've been planting them on July 4th and that timing seemed to be right, at least in 2006 it was. Thank you!