Hi mkinsey,
It is possible to do what I think you are are asking for by using the extension SQL 2 Excel Pro (you may be able to use the free version - but it is such a good product!).
The follwoing SL statement would do most standard (no custom fields) for an event with both individual and group registrations. The only item you would need to change is the event.id which in this case is "11". Each Event has it's own id.
SELECT jos_dtregister_user.eventId, jos_dtregister_user.userId, If(jos_dtregister_user.userType='G',jos_dtregister_group_member.firstname,jos_dtregister_user.userFirstName) AS forename, If(jos_dtregister_user.userType='G',jos_dtregister_group_member.lastname,jos_dtregister_user.userLastName) AS surname, jos_dtregister_user.userOrganization, jos_dtregister_user.userAddress, jos_dtregister_user.userCity, jos_dtregister_user.userState, If(jos_dtregister_user.userType='G',jos_dtregister_group_member.email,jos_dtregister_user.userEmail) AS mail, jos_dtregister_user.userPhone
FROM jos_dtregister_user LEFT JOIN jos_dtregister_group_member ON jos_dtregister_user.userId = jos_dtregister_group_member.groupUserId
WHERE (((jos_dtregister_user.eventId)="11"))
ORDER BY jos_dtregister_user.userOrganization, jos_dtregister_user.userCity
Then, using the menu item relating to SQL 2 Excel and the plugin which allows SQL 2 Excel content within an article, you can have as many event reports in the front end as you like including downlaods of spreadsheets and all controlled by the Joomla permissions.
Even if you are not an SQL guru (and I am certainly not) and you have custom fields, it shouldn't be too hard to see where they go.
Regards