Hi!
I have a suggestion. I find it odd how Preston sends you halfway across the map for your first mission. Instead, I suggest he should send you to Abernathy instead. The dialogue there would also be more fitting (bottle caps?).
Also, for further missions he shouldn't be sending you to the other end of the map, when you haven't even been in the area one way or the other. For example, I was sent to the far south once (forgot the name) when I hadn't even reached beyond Diamond city.
cheers,
M