Yes, they'll let you. The boarding-pass-checkers at LAX Terminal 5 are pretty, err... lax when it comes to things like this. You can also usually get into Terminal 5 with just your Crown Room Card if you have no boarding pass, and you can usually get into Terminal 6 with a Terminal 5 BP and vice versa if you just tell them you're going to the airline lounge in the respective terminal.

Continental's PC doesn't close until 1AM (compared with 11:30 for the CRC) so I use that when flying out on the 1:45 redeye to DFW.