To move my comment to an answer,
Live, in "Live más", is in the imperative mood. The imperative mood in English can only take the first- or second-person. (In Spanish the imperative third-person is simply a formal or plural imperative-second person—it is still addressed to the second person, though conjugated for the third.)
The imperative first person is generally (always?) first-person plural: Let us live más. I will gladly take correction, but I can think of no case in which the imperative first-person plural that does not employ "let us" or "let's". If the verb is alone, it must be second-person.
Live más could then be imperative second-person singular or second-person plural. English does not distinguish these two conjugations.