Which address to state as my own at top of publication?
Many templates include a place for authors to put street addresses, but they aren't necessarily strictly required. 

In your case, if you look at last year's CHI proceedings you can see that plenty of papers omit it.

For your submission, communication related to your submission will be via email, not snail mail. You can either omit the address entirely, or put the address of your computer science department, it doesn't really matter much. (In the general case, I think it's likely that if a publisher does want to communicate by snail mail, they will ask for the preferred mailing address in the paper submission process, not read it off the submission.)