For Instant Search or Advanced Find? Not automatically for either.
For Advanced Find you'd add the fields using the Advanced tab to add user
defined fields in the folder (the user properties must be added as folder
properties and not just in the items).
For Instant Search you'd use the add criteria setting to add the form the
user properties are from, which makes them available for Instant Search. The
properties must be from custom, published forms in that case.