You can take it while on cycle. In fact, your body is in such an anabolic state that it is soaking up everything so you get good absorption.
I however, like to wait until the end or right after the cycle. The reason is because when I start taking creatine, within a few weeks I always put on 7-10 lbs. These pounds will help to offset any potential losses due to the discontiuation of the AAS.
Now, obviously some of those 7-10 lbs is water but I also notice considerable increases in strentgh and muscle density.
note: I like to use old school pure creatine monohydrate. It typically creates more water retention than products such as cell-tech etc. I dont mind a little water weight. I seem to look better and fuller. (IMO)
Hope this helps.