Yes... from the CMS (/admin)... workspace. You will see a link to the properties.xml file.
When you click on that it will take you to the /SYSTEM/conf folder... scroll down until you see the properties.xml file and edit it.
You can update the following line...
<Property name="applicationApprovalRequired" value="no"/>
FYI, you can also set the registration to auto approve also...
<Property name="registrationApprovalRequired" value="no" />
Once you save the file... be sure to publish it. I don't think you will need to restart the portal for this to take affect.
Hope this is what you were asking.