I haven't been, but today on KPCC Larry Mantle was doing a 2 hour report on long beach speaking to various city and community leaders. He spoke to Cambodians who make up 10% of the city (fact - 33rd largest city in the US).
In any case, one of the Cambodian speakers mentioned this place as a really good place for Cambodian food. And I found that it has a website.
I know very little about real Khmer food except for a very interesting NEw Yorker article back in 2000. So, if anyone knows it or wants to try it here's the link. The menu on the site shows lots of Chinese borrowings so that may be either, 1. what they serve to everyone, or 2. evidence of an English language menu for non-Khmers and a possible all-Khmer "secret" menu.