Computer level managed preferences will unfortunately always apply regardless of user, however with user level managed preferences you can create seperate managed preference profiles for your different users (this will only work with AD users), and scope them each to the user groups you want them to apply to, or if you'd like no managed preferences for your admins scope your single user level preference profile to a group that does not include them. There would be no way to stop the machine level preferences from applying even to the local admin though.
