bavaria - You said to only use cash, but is there an issue using card, when it's accepted?
In Europe we carry cash far more than it seems people do in America, because many places do not take credit cards, or as I said, if your card does not have a chip it will not work in various machines.
If you are ONLY going to DLRP and only going to major hotels then you won't need much, but if you plan to buy groceries or go to a bakery or a museum etc then you should carry cash. You will also need cash many places to use the restroom.
Using a cash point outside of your network can result in high charges - up to $10 for instance for 'foreign machine' usage, on top of any fee charged by the bank servicing the cash point. That is why I strongly suggest checking with your bank for agreements. I travel about 300 or more days a year around the world and avoid fees by staying within my Deutsche Bank/BNP/BoA/Scotiabank/CCB etc network.