There's an old story about mexicans landing in the elbe mouth area around 60 bc, but the original account makes it basically certain that they were from India.
"When he [Celer] was proconsul in Gaul, he was presented with certain Indians as a present by the king of the Boti; asking whence they had come to these lands, he learned they had been seized by a storm from Indian waters, that they had traveled across the regions between, and at last landed on the German shores"(Pliny).
This indicates that their language was at least known.
I don't see what in this short account makes you think they might have been Mexicans.
The language bit, however, is not certain. They could have learned the language of a local Germanic people and used it to communicate with the Romans (via interpreters I'd guess). India was relatively well known to the Romans; I suppose they would not have called "Indians" people that were clearly totally different from actual Indians. Perhaps they would have referred to them as people from less known areas such as Chryse or Serica. OTOH, Chryse (likely what is now the Malay Peninsula) COULD have been considered "India" in ancient Roman geography (and in later European ones, of course ).
However, Pliny was of course aware of the Earth's true shape, so that "regions between" might be a reference to the Ocean, either crossed directly or through a *Northeast passage. I don't think it's a likely interpretation, since news about the possibility to cross the Ocean directly and staying alive would have likely made a sensation even at the time.
A *Cape Route was known to be at least theoretically possible, so seems the most "normal" way interpretation in Roman eyes. One wonders, however, if the account is true, how they actually got there.