Challenges faced when fluently speaking 2 languages in one sentence

So this is a spin off from Sperk's comment in this thread http://masterrussian.net/f16/our-gen...42/#post215373

Quote:

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Originally Posted by sperk

So, they'll bend over backwards trying to pronounce some French players name properly then take a break before returning to "Paris".

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Now I know that was a bit of a joke but in reality it can be hard to speak two languages in one sentence and not get mixed up and get your accents correct.

I have an example of something that seems very simple but is actually very difficult.

In this radio spot (in Spanish) the American Corporation wanted their name said in English but as they use an acronym (or would it be an initialism), they wanted each letter in Spanish and then what each letter stood for in English. As soon as you say "Security" you want to switch back to English and say I, not E, and after you say Protection you want to say AND!

SiPC El Finalista Radio

I am always amazed at the newscasters who CAN switch back and forth with such ease and perfect accents.