We check this website, now yelp.com.hk is up and dont blocked for our system and other users of the Internet.
So, answer to question: Is yelp Down Right Now? - NO! yelp is up!
If you have problem with access to site yelp, and domain yelp.com.hk is not avalible.
Clear browser cache and/or try other web browser
(Chrome, Firefox or Safari).