Definitely possible. You need to add the appropriate settings to the site.ini for the front end siteaccess.
[UserSettings]
# Where to store newly self registered users
DefaultUserPlacement=12
# Which section to place newly self registered users
# (Using 0 means that the user will get the section ID
# from its new location)
DefaultSectionID=0
# Which content class to use for user creation
UserClassID=4
# Which content class to use for user group creation
UserGroupClassID=3
# Which class group that has user classes, controls which classes
# is shown on the user navigation part. If empty all classes are used.
UserClassGroupID=2
# Which user is considered the creator
UserCreatorID=14
Of course change the UserClassID to be that of the class id from the front end user content class and any of the other settings if required.
The default entries will continue to be valid for the admin siteaccess.
