I bought a MIFI jobbie from Amazon and with Vodafone I get to take my UK data allowance abroad (including Turkey) for £3 per day. I know this isn't exactly relevant to the question in hand, but just to say the signal in Calis and Fethiye was excellent. I would normally go and get a Turkcell sim in Fethiye but this saves all the hassle of that, works on arrival and doesn't end up with my phone/MIFI being blocked when we return.