We are not talking a Mad Max scenario where the only currencies left are gas, ammo and pussy, but a possible hyperinflation.
In that case, gold would be awesome.
Also, if you have to travel fast to a place that actually has an economy left try to transfer money without the government noticing whereas I can garantuee you that you can put quite a bit of value up your ass in the form of gold and diamonds.
If the point did not get through, I can try to put in even more blunt terms.
My country has had 4 currencies in the last 100 years and the last 3 went to shit lightning fast when it happened.
Oh, I forgot, shit like that does not happen in America, expect that it already did.
edit: Sorry, we have the fifth currency now.