Yes. To link to the join page use the following:

http://www2.PANCHODOG_SITE.com/signup/signup.php?nats=YOUR_LINK_CODE&step=2

EXAMPLE:
If you wanted to link directly to the join page for AndiPink in you could use the following:

http://www2.andipink.com/signup/signup.php?nats=YOUR_LINK_CODE&step=2

Note: Be sure you change 'YOUR_LINK_CODE' for the appropriate linking code.