Here are the steps.
1. Selection by Query
2. Choose Criteria
3. Scroll down, and click on the +
beside the Wall option
4. Choose Alignment
5. Choose Left
6. Choose Save
, and give it a name... and choose OK
7. Click on OK
to run the query (all your walls that are left justified will now be highlighted
8. Right click and choose Properties
, choose Wall
... then change Left
Go through the same steps to change the right justified walls to left justified (just choose Right instead of Left in step 5).
Now each time have a drawing you need to do this with, you can just pick the query you want to run from the Named Query List, run it, and do step 8. There is probably a way to use he Macro Recorder to do this too, but I'll leave that up to you.
I hope I didn't miss any steps... so if this doesn't work, let me know and I will go back through it