In Star Trek: First Contact, when the Vulcans come to Earth and meet Dr. Cochrane, the one very clearly says "Live long, and prosper."

But how would the Vulcans know how to speak English? Up until this point they considered mankind to be 'too primitive' for first contact, and likely wouldn't have bothered to learn any of the languages from Earth. This was also about 90 years before the creation of the universal translator. So how was it that they were able to communicate with Dr. Cochrane and the other humans?