It doesn't currently have any functionality like that. The pay later feature was requested a long time ago and I basically implemented it to support the scenario for like a course where the user would bring a check or make payment at the event.
I could easily add a setting where text could be entered that would be appended into the confirmation email if the order is a pay later order. For now you could use a custom email template for the confirmation email and just hard code a message in there saying that if you chose pay later please mail your payment to...
By default the email template used is /Data/MessageTemplates/en-US-DefaultOrderConfirmationPlainTextEmailTemplate.config
You could create a custom file say named like en-US-MyCustomEventCalConfirmation.config, copy the contents from the default one and then modify it. It only support plain text for now.
To make it use your custom file add this to your user.config
<add key="EventCalProCustomConfirmationBodyTemplate" value="MyCustomEventCalConfirmation.config" />
Note that you leave off the en-US- in the config setting even though the real file name starts with en-US-
Hope it helps,