First thing I would do is go to Wal Mart and talk to store manager and see if it is even allowed. Wal Mart corporate policies are strict.

If Wal Mart is a no go then try other places like Lowes or Grocery chains. Use selling point to manager that you will rent space and another advantage to the store that people that stop to look at cars might go into store and buy something.

If you do land a spot to do this then advertise in penny savers about the sale

Mark