Istanbul getting money from atms

It's far better to get your cash from ATM's. Change bureaus give you a terrible conversion rate. The only charges you'll incur using an ATM will be those imposed by your own bank or credit card company back home..

First, I would suggest that you go to another place on this web site: Graffiti Wall, scroll down to Money/Communications and click on ATMs:Minimizing Fees.
Your question is usually asked daily on this web site and the other web site location can give you lots of information if you have not gone there already. I spent parts of May and June in Istanbul this year and relied only on getting local currency from ATM machines with one of my two debit cards. My primary debit card (from a local credit union) showed a 1% service fee for each transaction. No fees were shown for the local ATM machines but that does not mean that they were not built into the exchange rate. Changing US money into Euros and then into TL (Turkish Lira) gets you two change fees which you want to avoid unless you have leftover euros from earlier in your trip. Many prices in Istanbul were listed in euros and TL. Our hotel listed a euro price but accepted all of our remaining TL as we were checking out to leave the country. I would also suggest that you get Rick Steves Istanbul guide book if you do not have it already. It had many helpful ideas that we used when in Istanbul.

To expand on a point Charlie made, the official currency of Turkey is the Turkish Lira (TL). While the actual exchange rate is about 1.9 TL to 1 Euro, merchants round that off to 2 to 1, which equates to adding a 5% surcharge. Prices are often posted in Euro, so keep a sharp eye out for that least you be surprised when it comes time to pay. Hotels often quote in Euro, but tend to use a rate close to the actual rate when computing how much is owed in TL. Your best bet is to make all cash purchases in TL.