Do the vendors accept access food cards (good stamps)

The only vendor to currently (as of 08/31/19) accept any type of government program is Beaver Dam Produce. They accept WIC, but only for Local Produce. All other Vendors were asked, but none accept anything at this time.

Food stamps

It could likely vary from vendor to vendor. I've seen some farmers markets where only a handful of them do.

I would call them ask them. You can google the number.