The only thing I'll add to BJ's post is been there, done that. Reality is you can get into the IAD IFL (I had the same itin as the posters, only via SFO). Also, on the return, if the lounge is in the terminal you're in for your domestic flight show your bp, and you can get in. This time its not been my experience since I haven't had the opportunity, but other folks I know going via LAX.