It's not a particularly bad time at all to be in Saipan, as long as a typhoon doesn't hit. Are you a non-Japanese speaker? Most of the dive shops there cater to Japanese (makes sense, as the vast majority of the divers who go to Saipan are Japanese). There are only one or two shops which will cater to non-Japanese speakers, which may explain why you have not received any replies. I did a quick check, and the only shop I was 100% sure that they catered to English speaking divers (Abracadabra) had a defunct website! Sorry this isn't much help.