Actually, while many of the private vendors accept cash only, almost all of the professional vendors accept cash, checks, PayPal and credit cards.
More and more of the private vendors are also accepting PayPal since it is so easy to transfer funds. I've often had someone purchase from my table at a show that way. They are standing right in front of me as they use their cell phone to PayPal transfer funds directly into my PayPal account. As soon as I see that the funds are deposited by using the PayPal app on my cell phone, I give the buyer his purchase(s), we shake hands and that's that.
Pipestud