Целую vs. До свидания

[krepsen.livejournal.com]

Can you say "Целую"  at the end of a letter to a friend instead of  "До свидания" ?

How to write....

[krepsen.livejournal.com]

I'm going to write a letter to a pen pal of mine in Russia. 
At the postoffice they said that the letter would arrive faster if I write the adress in russian. 
 The name of the street is "Libnehta st." I'm doing fine in writing the adress in handwriting until i get to the "h".  Now some places I've read that the russian letter "х" is the same as the english letter "h" is this true?
Could someone please tell me or explain how I should write the streetname in handwriting?
I hope you understand my explanation:)

Thanks in advance!

CORRECTION: the correct street name is "Karla- Libknehta st"
Is it correct that it in russian then will be "Карла Либкнехта ул." ?