If you have a smart phone along with you, you can still 'upload' data only packets (20tl/1GB or 40tl/4GB or 80tl/10GB) to your local SIM card and turn the Personal Hotspot feature on your phone (it is very simple with iPhone, but should be just the same with other smarties).
If you have an 'unlocked' smart-phone (using SIMcard technology -in US AT&T does, Verizon does not-) from your country of origin, you can pop in a local (TurkCell, Vodafon, etc) SIM card that will work for about 30 days+. After that you have to go through the headache of 'registering' it with the communication authorities. Assuming you are coming as a tourist for 3 weeks, you can get away with it without investing in a 265tl WiFi device.