I used to live in Beijing, and often flew other airlines. I was NW Plat, and always just showed my Plat card to enter. It shouldn't be a problem-- the attendant just writes down the number and you get in. If you're not a WC member (or Asia-Pacific Gold or Plat) then you probably can't get in unless you're flying WBC.
But to be honest, the club is substandard compared to other NWA clubs.....poor selection of snacks, drinks, etc. And usually no English papers, except the China Daily. And if you've ever read that, you know that essentially it's an 8-page propaganda sheet.
So, long story short, if they don't let you into the CA lounge, you're not missing much.
The lounge that UA, MH, and TG have access to, closer to the gates, however, has hot foods, and a much better atmosphere. So if you can get into that one, enjoy yourself!