Hi, everyone has their own way of doing this. I prefer to always have Euros with me. Just easier than having to find a bank/atm, etc. I travel solo it is the last thing I want to think about so I just bring them and I usually have some left from previous trips. To the OP, you asked if "most places take US $?"...no, they don't. Think of it this way, if someone was coming to the US, I don't think any retailers would accept foreign currency so I would not think countries in Europe would take it either.
The only place I have visited that take US $ is Turkey......they accept all forms of currency. Euros, US $ and of course their own, Turkish Lira.
But the other countries I have visited do not take US $.