Would you take a six month old pup to a growers market?

It depends on the dog, honestly. Sam can be outwardly less reactive in busy crowds like that, but in retrospect I think he's often simply overwhelmed and not in a mental state to be actively learning from it, if that makes sense?

If you want to try it, my advice would be to find an out-of-the-way spot where you can see the activity but not a lot of it is passing close by. Sit with her and reward the heck out of calm behavior and any checking in or refocusing on you. You might have to be prepared to call it quits if she gets too worked up, though. Remember that it's the quality of the socialization that counts more than the quantitiy!

Thanks for the advice, that makes sense. I think if we take her we'll sit in a quiet (relatively) part of the park where people sit and walk through but aren't all jammed together. Also I'll bring some high value treats that she hasn't had yet, yay string cheese. We have a friend who lives nearby so if everything gets to be too much we can take her to his house.
Thanks again. Sometimes it seems like this should all be common sense but it's been a long time since either my husband or I have raised a puppy.

I actually don't think it's all common sense! And there's so much conflicting information re: socializing, too. I certainly had to find out by making mistakes... and now I've no doubt I contributed to Sam's current frustration reactivity by allowing him to meet all the dogs in the name of socialization. It can absolutely be a tricky balancing act between what "good" and "bad" socialization means for your dog.