It might be they reply in this way because I am talking nonsense as they claim.
Your heading in the right direction.
Or it might be that by i) mentioning safety and ii) dicussing scenarios involving lack of communiction between staff and passengers I am mentioning something which "everyone knows about" but "polite" people prefer not to think about.
i) You'll find that crew quite often discuss safety/scenarios/Procedures/recent incidents on a regular basis. We're not afraid to discuss it.
ii) I can communicate well flying across Europe and North Africa and have few real issues. A little bit of Spanish helps me from time to time but believe me I reckon communicating on cabin service to be more challenging than communicating in an emergency. As you have already been told, emergency communication is predicated on short, sharp positive commands. With that in mind imagine yourself trying to communicate with someone who doesn't speak your language. a) trying to sell them a drink and a snack and b) Giving short loud commands with gesticulations (i.e actions). The former requires alot more conversational skills where as the latter needs minimal of that. I guess what I am trying to say is..... there is no issue.
I can't think of an incident where the language barrier was cited as an issue.
When I read the safety card and listen to the safety brief (as I did for the last time about 10 days ago) I do always wonder whether it is meaningful since if we slam into the Pyrenees we are unlikely to need our life jackets, with or without whistle and light, irrespective of whether the jacket itself be fully or partially inflated.
Considering the Pyrenees are a mountain range you are wise to point out that indeed lifejackets would be of little use. However if the aircraft was in the nearby Med or Bay of Biscay then the lifejackets may be of some use. Of course everyone cites the impossible nature of ditchings but there are examples of success in addition to aircraft overshoots etc at many of the worlds water edge airports.
If however the information there might just be helpful to my family and I whether a few hundred metres east from BCN or on the tarmac at LHR, I am not convinced that the meaning and the content of shouted instructions and advice will be self evident to all passengers, especially non-English speakers, as the water laps around the door or as the choking black fumes fill the cabin.
Crew commands work in conjunction with other safety procedures and equipment. Lights for instance are designed, in no small part, to help passengers in smoke filled cabins and if you are in a position where water laps around the door, your ditching will have been relatively successful. This is where you would see crews training kick in and the language barrier would be barely existent.
On the other hand, should there be four or five hours available to evacuate the plane, as with the Costa Concordia, then my fears are obviously groundless as mime and improvisation will be available to supplement the unfortunate lack of language skills and EU regulations demanding them.
Again you'll find that most incidents where evacuation takes place, passengers are evacuated exceptionally quickly.
Now I've never said that language speakers aren't handy. They are. Certainly at my airline they can really make things easier. There are lots of speakers across the UK network it's just not prudent nor practical to specifically roster them to particular flights. At out Continental bases they are required to speak the local language but pre-flight briefings, security and emergency procedures & commands are required to be spoken in English.
Think about airlines, particularly hub carriers, who also have multiple languages that originate from no where near where the flight originates or destined for. As examples, In theory both the US A320 in the Hudson and the A343 in YYZ are likely to have had passengers who's languages weren't represented on the crew. Despite that both evacuations were pretty much text book! Remember also that both of those incidents were what we call "unplanned emergencies' which basically means there were no preparation time and so those passengers had just the commands to rely on. There is no reason to suspect they weren't understood.
But even if you have a flight with a language speaker and even if it's on a small/medium jet like the A320, it's not always useful if you're at the rear of the cabin and the language speaker is at the front.
It's incredibly hard for an airline to make money especially when people have an unquenshable thirst for cheap fares but despite the cost cutting I am pretty confident that most airlines and regulatory authorities take safety very seriously and my airline can actually be quiet anal if truth be told. With that in mind I am sure the concerns over the language barrier have been discussed and looked into and deemed to not cause a safety issue.
Do I sometimes wish that we (Brits especially) were better at languages? Yes I do but as more of a courtesy rather than due to any safety concerns I have.