You could probably skip Zippy's as noted above. It really isn't that special.

I'd probably consider going to Shirokiya as they do offer decent Japanese food for a cheap price.

You should probably go to Legend Chinese Restraunt at the Chinese Cultural Plaza in Chinatown. Easily reachable by bus. I love the fried cake noodles. Nice and crunchy.

Spam is very popular here. Probably moreso here than anywhere else in the USA. Try eating a spam musubi.

Agree with above that Kalua pork and cabbage is very good as a plate lunch item. I like Garlic Chicken too.

Another local delicacy is haupia, a sort of firm coconut pudding. Probably won't see this one anywhere on the mainland.