If you are talking about dive operators, you don't care about the dive op itself being close, some will not even have much of a place on land. You're not really interested in getting to the shop - you're interested in getting to the boat. Boats leave from a few different marinas and other locations, and you may not even leave from the same place everyday, depending on the op and where you are diving. You just need an op that picks up where you are staying, which will be pretty much anyone that caters to that side of the island. They may or may not stop at their shop on the way to the boat, depending what's going on. So pick out the op that you think you will like and then make sure location/pickup works, and don't worry too much about location. Look at Divetech, Off the Wall, Ambassador, Wall to Wall, Divers Down, Neptune's for a start at some of the smaller and better ops.