Couldn't this also mean "The woman and the men didn't speak"? Since the vowel -ī at the end of valī could also act as a conjunction of two similar grammatical units. Or is this just something that context will make clear?
Yes you are right. It depends on stressing rather than context though. If it is the "and" meaning "valī" would be stressed at the ultimate (valĪ) while if it is an accusative, object to the verb it's stressed regularly (vAlī). Audio makes it clear.