Yes; from a quick web search, here are some cases where they did:
November 30, 1999: Jordanian officials successfully uncover an al-Qaeda plot to blow up the Radisson Hotel in Amman, Jordan and other sites on January 1, 2000. [PBS Frontline 10/3/02] A call between al-Qaeda leader Abu Zubaydah and a suspected Jordanian terrorist exposes the plot. In the call, Zubaydah states, "The grooms are ready for the big wedding." [Seattle Times, 6/23/02]
This call reflects an extremely poor code system, because the FBI already determined in the wake of the 1998 US embassy bombings (see August 7, 1998) that "wedding" was the al-Qaeda code word for bomb. [The Cell, John Miller, Michael Stone and Chris Mitchell, 8/02, p. 214]
Furthermore, it appears al-Qaeda fails to later change their code system, because the codename for the 9/11 attack is also "The Big Wedding." [Chicago Tribune, 9/5/02] US intelligence claims it failed to understand the code language for the 9/11 attacks.