There are three (four if you count educational postings, ie NPS) types of postions for IWOs: shore, DIRSUP, and PCS to carrier/small boy/gator.
Shore: most likely to be sent to one of the big four mentioned earlier as a JO. As rank increases, there are some other possibilities. (Staff, R&D, smaller commands, etc.) I would not state that an IWO can go anywhere in the world. He/she can if aboard a ship/squadron, but there are fewer exotic postings than from times back.
DIRSUP: based with a team out of one of the shore commands and sent on an as-needed basis. Someone earlier had referred to them as the backbone of the IW community. I would probably have to disagree. They are very effective, but the work is pretty much carried equally with the others.
DIRSUP is also mission-specific. When they are not needed, they go home.
PCS: Usually two year rotation to ship/squadron from what I have seen.
And sometimes I see people do a mix of DIRSUP and shore jobs. Also with IAs, we often go forward to do a variety of in-job/out-of-job positions.
In terms of each individual location (TX, MD, HI, GA) don't worry too much about mission. I did, because I was a linguist and wanted to stay with what I had background in for my first tour as an officer.