How do you say Novac ? Is it like VACuum or VACant ? my friends say the locals say VACuum,
but its just shortened " No Vacancy " so i believe it would be said VACant.

Personally I prefer VACuum, though as you said, it's derived from "no vacancy" so it should be VACant.

Nov-Ack.

Novac.

Just because the original sign said 'No Vacancy' doesn't change the rules of the language. The second you cut off the ancy, the emphasis of the whole sign changes, and the first (and now only) 'a' changes, making a short vowel sound.

^This^

Besides, Nov-ache just don't sound right when spoken.

I pronounce it the same way Mr. New Vegas does.

N?ov??k.

Personally, I pronounce it 'Throatwobbler Mangrove'.

But then again, I might be a bit bent.

Let's assume the 'bent' part of that...

... Mangrove? Really? I didn't even know anybody knew what those were anymore... -_-;'