Rodger Winn and 'Working Fiction'
What is often forgotten in this whole argument is often the communication decrypts are incomplete or missing key details. The decrypts supplement a through understanding of the strategies and tactics being used, traffic analysis, good old fashion intuition. Sir Rodger Winn called his daily analysis of the German U-boot efforts 'working fiction' because he realized he was always partially in the dark about the true German intentions, even when Enigma decrypts were available.
In the movie 'Tora, Tora, Tora' there is a scene were Col. Rufus Bratton was puzzling over the Japanese diplomatic messages and other information. He concluded the Japanese were going to attack on Sunday 30-November-1941; only 1 week off. The US at the time was decrypting Japanese diplomatic messages as fast or faster than the Japanese Embassy in Washington at the time.
The issue is not have the decrypts but having the full context of the messages. Also, depending on how much planning took place 'off the grid', the decrypts may not make much sense to someone not part of the plot. Given San Bernardino was a husband and wife team, I suspect most of the planning was face to face. Also, activities that should have raised an alarm were not reported because many feared being labelled a racist if they made a report. However traffic analysis would show who they were communicating with and that would warrant a visit and game of 20 questions. Most would be absolutely innocent.