Thanks Gokuyum for this very fast translation!  (And now wondering what I have to think of this note....  

I am not a native English as you probably could understand but I think a question mark isnt too necessary. I think it can be:

can you please let me know when you arrive ?

and

can you please let me know when you will arrive ?

So like İ said the translation would be:

Bana ne zaman varacağını bildirir misin ?

(or actually bildirebilir misin because of the ´can´ )

Other wise I think Sam would have written:

Can you please let me know when you´ve arrived ? (But melike the action of arriving has finished at this sentence, but in my translation it hasn´t finished even it hasn´t started. Vardığın zaman means also varacağın zaman (in this context) in Turkish. Think Turkish way, you will understand me. But also there is difference between "Varacağın zaman bana bildir." and "Varacağın zamanı bana bildir" Varacağın zaman, bana bildir means "Let me now when you will arrive." Varacağın zamanı bana bildir means "Let me know what time(when) you will arrive." I need a question mark here i can´t know which one is which without it.

The note I got today from a friend is handwritten and I had difficulties to decipher his handwriting. Any spelling errors are likely mine, not his.

I only understand in this note ´my angel´, my devil´ and ´my fire´, so can anyone please translate it for me? I´m very curious to know what is says. Teşekkürler in advance.

Meleğim olmanı istedim

I wanted you to be my angel 

Sen benim şeytanım oldun

You became my devil. 

Sonucta ateşimsin

Eventually you are my fire 

Uzaklaşsam donarım diye korkarım

I am afraid of freezing if i become distant 

Yaklaşsam yanarım diye korkarım

If i draw near you, i am afraid of burning 

I think this should be:

Bana ne zaman varacağını bildirir misin ?

Because how you translated it Gokuyum, it means: when you´ve arrived (past)

And the question was: when you arrive (so when you are going to arrive, (future)