We did the same in July!
Driving back from the Grand Canyon to Las Vegas we went through the Navajo region and Zion National Park Utah. Stopped off at the side of the road, had a bite to eat in a shack (paid by AMEX)then went to a picnic table containing handmade jewellery. Paid by Visa!
It was the strangest thing i've ever seen, this little Navajo tribe fella producing his credit card reader!!
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