How do you say it in French? Italian? Spanish? Portuguese? In ... blah, blah, blah?

Really? Do people really talk like that? In what language do YOU use "blah, blah, blah?"

When writing, "etc." comes to mind, but I would never write "etc., etc., etc."

In Italian you say it "et cetera, et cetera, et cetera"

the "c" is prouncounced like English "ch"

Bla, bla, bla is used in colloquial Spanish.

"Bleh, bleh, bleh..." is often heard in french. (At least that's how I'm assuming it's spelt!.... ah, yes it is - Mme DoGood confirms.)

I don't remember hearing "bla bla bla" in Spain, but my friends and I use the following a lot:

a hand gesture involving imitating a mouth while rolling our eyes.

"tal tal tal" (for example: Y la tia estaba alli hablando. . . tal tal tal. . .ya sabes"

"la la la" (I use this a lot with my host family, particularly my little sister, when they are running on and on)

Three short exhales and a rolling of the eyes is also a big one.