In the event of rapid inflation, the most likely scenario with the massive deficit spending we've got coming up, sticking your money under the bed won't protect you much.
The idea that foreign currencies will be a safe haven is based on the not necessarily well-founded assumption that other countries won't have their own problems. In actual fact, most countries are more corrupt and have bubbles going on that are at least as large as those in the USA.
In Europe, for example, the media is even more corrupt and complicit in the conspiracy of the elite against the populace than it is here. Their real estate, believe it or not, is priced much higher than the average in the USA. Any commodity where the price rises much faster than the income of potential purchasers is headed for an eventual bubble burst.
If you're going to stuff money under your mattress, make sure it is US dollars, it's still safer than all others.
I've saved some food and especially coffee and chocolate. (Along with some Krugerrands I bought in 1993, guns and ammo bought during the Rodney King riots. So...)