I went to France for a week 4 years ago. Same situation, didn't need to pay for bfast or dinner. I took 1000 dollars. Didn't spend it all (well travelers checks, I didn't have a debit card then).
If I were you, convert over 100-200 Euros now. Incase you can't find a conversion place real quick over there. My first day in France I had 10 Euros. That got me lunch and nothing else.
Next, get a debit card if you don't already have one. Call your bank, alert them that you will be traveling to Europe so they know to allow money out overseas (some banks won't allow overseas withdrawals due to security).
Put 200-500 (more if you like to shop I guess) in the account. When you withdraw money from the ATM in Europe, it will come out as Euros.
So 300-700 depending on how much fun you wanna have, what your taste it, how rich you are, etc. no less than 300 though.