This place is as legit as it comes...
I live in North Phoenix near Desert Ridge and I often go down to Mesa to eat at Best Hong Kong on Southern and Dobson. Now, I hardly go there not because I don't like the food but because I can get another dish with the gas money I save by going to King Wah!
If you're a fan of bitter melon, ask for a special dish made of bitter melon, beef, and egg. It's a legit HK dish that not too many restaurants make but King Wah will do it for ya. :)