I would not be surprised if wireless internet access is a reasonably common in Istanbul but as I have not been there for a while I haven’t seen it.

The first time I recall wireless internet access anywhere in Turkey was at the Otantik restaurant in Antalya earlier this month.

I now read that the Kamil Koc bus company will add free wireless internet access to their buses (registration required):

A deal between Avea-partner Astech and Kamil Koç has led to new wireless Internet service on Kamil Koç buses, which will enable passengers to surf the Net free of charge on personal laptops while traveling. The Speednet IP9200 connection will offer nonstop connection on buses, despite rules that cell phones not be used on board. It was not specified whether the deal will remain exclusive to Kamil Koç.

Kamil Koc is one of the major Turkish bus companies. Unfortunately they do not serve Mersin.

I will buy a laptop computer soon and wireless is one of the features the computer will have to have. Go wireless!