In the SalesLogix Customer Portal web site, only certain groups are visible.  There are two factors that control access to a group in the customer portal:

1. The group must be released to the SalesLogix user that is used for the web access definition. 
2. The group must have CUSTOMERPORTAL in the DATACODE field of the plugin table.  There is no way of updating this field other than via a back end SQL statement.

One these two conditions are met the group should show up for you in the customer portal.  You will need to log out and back in to see it and possibly to do an IIS reset if the groups are cached.