During past trips in Europe while charging items using my visa card I have been asked by the merchant if I would like them to charge me in american dollars or the currency of the country. I will be leaving soon for the Turkey tour and I have always had them charge me in the countries currency, is this still the the best way to go? Thank you.
Yes, it absolutely is.
The option to charge you in US dollars is called "dynamic currency conversion" or DCC, and it is essentially a scam, as they invariably charge you a horrible conversion fee. Always, ALWAYS pay in the local currency. And watch out - DCC is both spreading like a plague, and it's also being slipped in quietly by merchants if you are not paying close attention. I've had it snuck in on bills even when I clearly and specifically said I wanted to pay in local currency, not in US dollars. IMHO, DCC is the most common way to rip off foreigners.
You should have and use a credit card that does not charge foreign transaction fees. There are plenty of these available, make sure yours is one of them (or get one that doesn't charge foreign transaction fees). Also be sure to call your banks (for any credit and debit cards you will be using) to let them know you will be traveling overseas, so they don't block your card suspecting fraud.
While being charged in your home currency is pitched by the card networks as a "convenience" to you, the customer, it is only a convenience to the merchant as it makes more money for them. I am not against a merchant making what he can off a sale, but this strikes me as unfair to the customer.
The process, called Dynamic Currency Conversion or DCC, allows the merchant (or ATM) to use whatever rate they want when converting from local currency to your currency. The network rules say this can be as much as 18% in the merchant's favor over what the network rate for the day is. And if your credit or debit card company charges you international fees, you pay them on top of the inflated rate getting hit doubly.
Just say no. And if the merchant claims ignorance in how to make the credit card machine use local currency, walk out. They will suddenly remember. Or pay cash using the local currency you got from a local ATM if it is restaurant or somewhere you must pay for the item because you have used or consumed it.