There's this stereotype of Americans being monolingual. While there are many that don't fit that mold, there are still enough people who fit the stereotype. And while knowing a language might not keep away organized groups brazen enough to target their prey in public and unapologetic enough to do so repeatedly (my inner Mary Lazarus wonders if they're Catholic), anything to tip the odds in one's favor is worth learning.
The Count of Monte Cristo's Abbe Faria spoke about how he learned languages - he studied a small sample of words in a language, used those words to get his point across, and used what he knew in one language to figure out words in another related language.
There are countless modern-day and real-life examples out there on this learning process. Baby sign language videos for infants and parents are a place to look - they're adorable and (pun intended) handy for getting single-word/sign/idea messages through. These videos show how the spoken word from the parent connects to a sign that can be mimicked by a pre-verbal infant, which can then be used to communicate an idea from one to the other.
If there's a common thread among the examples above, it's that learning the basics works at any age. Below are a few categories and terms to consider learning in any language:
Greetings like hello, goodbye, please, thank you, sorry (which, depending on the language, might also work as 'excuse me' to get through a crowd).
Numbers, at least those from one through ten.
Basic needs and emergencies: food, drink, rest, hot, cold, bathroom, sick, hurt, help.
Basic directions: up, down, left, right, in front of, behind, next to, inside, outside.
Oh, fine, people too: parent, offspring, sibling, spouse, old, young, male, female. (Gender-neutral language may be a thing, but like it or not, gender-specific language exists too.)
From these building blocks, one can cobble together a crude message - such as "one old male hurt outside food one young male one old male two young female."
There are plenty of other possible additions to the above, and I think I have an earlier post that includes ways to enjoy learning the basics of a new language, specifically by using words that link to a favorite topic. Like music? Learn the lyrics to popular songs in a new language. Like food? Learn the names of dishes and ingredients. (There was a series where a notoriously cranky chef traveled the world to learn new foods. In one episode, he was jumping around a kitchen trying to sign the word 'star' in 'star anise' [star in the sky la la la la.] The word for 'spice' and a star shape with the fingers might have been more helpful.) Oh, and on that note, learning swear words and insults is always entertaining. (Muppets.)