You never know when you might need to say “Help, I’m dying” in a foreign country, and the sooner you learn how to say it in the local language, the better your chances of survival are.
However, your chances of survival don’t depend on whether you know the local greeting or not, since it’s mostly used in a casual conversation, not a life-threatening situation. Therefore, one should 1st learn how to say the phrase “Help, I’m dying”, and then learn the greeting.
“where are the toilets?” is the first thing I want to know on any language, and the phrase I know in the most languages.
A bloodcurdling scream is universal, and I have a good one. That seems a reasonable alarm phrase.