I do not think that ODS LAYOUT and ODS REGION will work with TAGSETS.EXCELXP. Tech Support could answer that one for sure.
If you switch to ODS and use an HTML-based tagset, then you MIGHT be able to open the HTML file with Excel and have the multiple tables respected. There is a tagset called HTMLPANEL, that will put HTML tables side by side -- it uses features of ODS LAYOUT and ODS REGION -- but since the result is "pure" HTML tags, then Excel MIGHT open the HTML file that you created with ODS HTMLPANEL. This tagset is not part of the installed set of tagset templates that are delivered with SAS and you would have to download it and read the documentation. I suggest getting it working so it looks good in a browser and THEN see how Excel deals with it. Generally, Excel doesn't like HTML 4 tags, so there's a chance that this will NOT work. Tech Support might know right away whether this is a good suggestion on not.
I was wondering if you had tried using "named areas" on the Excel spreadsheet?
This is where you basically predefine the format of the report in Excel and name the block. You can create any number of named areas, side by side, or even on top of each other. Then using SAS you simply write the data into the named areas.
Here is a presentation that I attended on how to do this...