I’d just like to interject that while traveling was rare in medieval times, it did happen. People usually didn’t get thrown in jail for it, even if they didn’t speak the local language.

Regular people didn’t really speak Latin beyond a few bits of prayer. The lingua franca was a mix of various coastal languages (think of the belter patois in the expanse), but even that was only known to traders.

You’d have a tough time for sure, but wouldn’t necessarily get in trouble.