Greece adopting Bitcoin is just not possible. The people may prefer it, but the government can't implement it officially. It is broke, it just cant buy bitcoins.
All the Greek government can afford to do is start printing Drachmas again if it stops using the Euro. It only needs to buy blank paper and ink. Buying Bitcoins would be immensely more expensive and would only work for computer literate people. Most countries, including Greece, have an aging population, many of whom are not computer literate.