"¿Cuándo viajas otra vez, Miguel?"
Translation:When are you traveling again, Miguel?
Yup. How are we supposed to know if the speaker is buddies with Miguel or not???
Here's my theory:
I was thinking the same, but then I realized the fact that if you're addressing someone formally, you often use their last name (like "Mr. Smith"). The fact that the speaker is using Miguel's first name would likely indicate that they are addressing Miguel informally.
Why not implying i will be travelling with him and asking for when? Viajamos....
In fact, a lot of verb forms would work: "When are they traveling again, Michael?", "When are we traveling again, Michael?, etc. all make perfect sense.