I spent much of my childhood in Greece, and thus around tourists from all over the world. In my experience speaking loudly and slowly reliably improves enunciation. It also often comes with exaggerated mouth shaping which gives useful visual cues that are interpreted subconsciously (see the McGurk effect [0]) but manifest in what you hear.

Obviously this isn't going to overcome complete ignorance of a language. But especially in touristy areas it's common for locals to know a few dozen words in several languages. My experience has been that people speaking loudly and slow makes it much easier for others to latch on to the few words they do know.

[0] https://en.wikipedia.org/wiki/McGurk_effect