Mailboxes have names on them, but not room numbers. You may have to check the mail one by one to see if anything clicks as being related to you or your mission.

One of the mail messages is completely unreadable. Or is it?

Check for extra letters in the message.

If you remove every third letter (all vowels), you will see there is a rendezvous at HBD. You may have to look around to see if you can find HBD.

There's a lot of helpful information in the flyers rack. A city map, a business directory, and yes, a flyer for the Hungry Bear Diner.

The business directory has addresses for all the businesses in Mercury Gulch. The Hungry Bear Diner being one of them.

Enter the street addres for the Hungry Bear - 640