A note on the idea of opening a bank account for a one month trip: forget it.
You need to be a resident of the country in which you plan to open the account. I needed to prove that I reside in Singapore, when I opened my account with DBS. I needed to prove I lived - permanently and legally - in the USA, when I opened my bank account there. And even in the UK, which has less red tape than some other countries (e.g. Italy and France), you will still need to produce a utility bill (gas, electricity, water) as proof of residence, if you want to open a bank account.
Regarding the cost of living there: as small as it may appear compared to China or the USA, Europe is not a country, it is a continent, with large internal variability. Do not expect to spend the same amount for a breakfast in Venice, in Bilbao and in Ulm. Also, do not expect to find people behaving in the same way across the continent: people living in large cities will often appear to be more rude and in a hurry (nothing new here, the same applies to non-European large cities, e.g. NY) than those in smaller cities.
As a rule of thumb, the most expensive place to eat is the high street of large touristic cities: move two streets aside, and you will usually get better food (less touristy) for less money. Beware of islands too: if it takes money to bring food (and other supplies) there, the end-user price will be higher. Remember also that "Chinese", "Indian", "Thai", and other "ethnic foods" there will be considerably different (and blander) from the original versions of those same dishes.
For those afraid of thieves: consider a backpack that opens towards your back. I use a Lowepro Flipside, and while it's a pain in the **** because I have to remove it from my back to open it, it's also reassuring that ... a thief would have to remove it from my back, to take anything from it.
And this brings to a last bit of advice: the safest backpack is the one you have on your back. Put it down, and you might as well put a "Thieves welcome" sign on it. So, keep it light, that will help you carrying it around.
Enjoy Europe.