What you prefer and what merchants prefer are two drastically different things. Cash is always preferred.

American Express is almost always the least preferred or accepted card out there when on SXM.

Visa and Master Card are probably the most popular followed by Discover and then American Express.

I recently used a Discover Card without issue at a couple of places. I also know many places refuse to accept any credit card and some specifically American Express.

To be safe, take a fair amount of cash and two different credit cards if possible.