Some do not take credit cards and I always look for the logos in the window

However if they have signs posted that say "$10 min for credit cards" or "$2.00 service charge added to all credit card transactions" is 100% illegal and prohibited practice by the merchant (restaurant) Basically they can not charge extra for the cost credit cards charge.

I work for a credit card processor and places that do are mailed a warning letter that they must sign and if it is a second or third warning it usually results in a $5 000 USD fine and or blacklisted by all credit card companies

so if you ever see places that charge that min/surcharge.. simply state that you refuse to pay it as it is a prohibited practice to the merchant agreement the restaurant signed and then call your credit card company up and state "so and so restaurnt refused to take my credit card without charging a minimum/surcharge"