Hi
Well, having spent a far bit of time in Pattaya, I'd have to first say that the diving is not that great. The main reason I go is that when I have been in Thailand thus far, I have some kind of business in Bangkok and have only a few days to spare, and it only takes 2 hours by car to get to Pattaya. Pattaya is also a pretty intense (and sleazy) beach area. For some that is a plus...There are a couple of wrecks and some nice coral spots but most diving is about 1 1/2 out by boat (far islands).
If I were to do a course like the one you are considering, I would go to a nicer area more known for diving, such as Koh Tao or Phuket. If you look on the Inernet, there are plenty of other IDC powerhouses out there, some even offer free room to IDC candidates. So look aaround, don'd presssure yourself into a quick decision.
Last, I think I have seen some posts by peole who have done IDCs in Koh Tao or Phuket. You should make a post like this, "Best IDC in Koh Tao or Phuket?" and I am sure you will get lots fo useful, first hand input...
Best of luck, sounds like a wonderful adventure ahead...
JAG