Dana, I don't get what you're trying to do. Not sure why you think you need the dual axis. It sounds to me like you really want to do something like what Noel did here: http://community.tableau.com/message/213963#213963
At the bottom of his post he offers to help folks trying to do the same thing. You might want to give him a ping.
I (think) one of the issues with polygon mark type labeling.
Dana, try to plot out the points using single-axis, and then format the background picture afterwards. Joe Mako has an excellent tutorial somewhere on the web...this might help too.
Hi Shawn, Allan,
Sorry I didn't get back sooner, other things took over. This is still outstanding though. Both your replies have good info on Polygon maps, but the reason I'm trying to do a double axis is that I want to use my values for the polygons and not have a fixed coloured background image and then on top of that I want to put text. Those two types cannot exist on one set of axis, which I why I tried with two