As to language.
The Hobbits spoke nothing but Common Tongue.
The Eorlings spoke Common Tongue to everyone not from the Mark.
Same for Elves. Same for Gondorians. Same for Dwarves.
So it seems like everyone new Common Tongue. I suppose that's why it's called "common."
Second point on language: Please same me a lot of time having to remind you and ask you to correct your posts. The people of the Mark don't say "Rohirric" or "Rohan" - those are Gondorian terms for them. They call themselves Eorlings, and they speak Eorling, and they live in the Mark.
Thanks.
Lommy, what does the letter say? Any ideas? It's from Athanar, right?