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.
I think it would be better to know the word to warn others of danger, because not only could you warn others of danger, you’d also be able to understand if they attempt to earn you.
The first sentence should be “excuse me sir, it would appear that there is a fierce rattlesnake behind you.”