Thank you for posting here in the Community, @AChipOffTheOldBlock. 

When creating a sales order, I'll provide some information about auto-populating a site.

Currently, neither the ability to auto-populate a site when creating a sales order nor the option to establish a default site location is available in QuickBooks Desktop. I understand that this would be extremely valuable to you and your company, so I've forwarded this idea to our Product Development Team. In this manner, the suggestions can be taken into account for a future update.

Feel free to fill me in if you need further assistance. I am here to help. Take care.