Currencies as part of travelling
Unless you leave within a monetary union such as the EU, you're going to be dealing a lot which currencies. If you time it right then you will be getting a good deal and might even save for a trip. Well that is true for certain currencies anyway. But some currencies such as the Euro or sterling are always going to be high and will be shocked at what you get for you money. Especially as living costs are not exactly cheap.
Certainly you can always change most notes, although if you have coins especially collectables like your kennedy half dollars then you're best hanging onto them unless you have a collector who is interested.
I often keep an eye on the currency market, so I am either getting a better deal or if a currency is expected to fall it is often wise to change them up before its too late. Especially in this economic climate.