Hi Lee,
In JMP you could use either Graph Builder or Bubble Plot to get what you are after. I assume your data has the lat / lon values. Use longitude as the x axis and latitude as the y axis, use total_visits as the size variable and use primary_store as the color variable.
To get a map you can set the background map option, which can be found by doing a right-mouse-click over the graph and select the background map dialog. The last option for image based maps is the Web Map Service. Enter the url you mentioned in the URL field, then enter us_interstates in the field called Layer. For the WMS server, you must enter a URL for the server and a layer name for the desired layer. Based on the picture you attached to this thread, it looks like you want to use the us_interstates layer.
Here is a link to a blog post I did about using the WMS background map option:
http://blogs.sas.com/content/jmp/2010/11/09/all-about-background-maps-in-jmp-9-nasa-server-and-web-m...
BTW - I see you are using the WMS Explorer add-in. That add-in was designed to help you discover what the layers are for a particular WMS server. But layers aren't always visible at all zoom levels. So you may have to zoom in on the US before the us_interstates layer will become visible. That is dictated by the WMS server, not by the add-in. Try zooming in to see the interstates appear.
Here is a link to a blog post I did about using the WMS Explorer:
http://blogs.sas.com/content/jmp/2010/11/22/all-about-background-maps-in-jmp-9-wms-explorer-add-in/
One last note of interest. In version 11 of JMP, just released last month, we now include another option for background maps called Street Map Service. Like the Web Map Service it uses a server to produce a map. But the Street Map Service uses a server provided by JMP. You don't have to know the URL or a layer name. The Street Map Service will produce a map with the appropriate amount of detail based on your zoom level. That will include all of the us interstates, once you zoom in on the US.
Here is what it looks like in version 11 with the Street Map Service:
I hope this helps. If you have any further questions please feel free to ask.
John Ponte