Lindsay,

Very often large art museums offer such tours to their members.  If you
were to contact various membership departments, they will be able to tell
you what their offerings are for the next season.  Many non-American
museums have signage and/or offer accoustiguide-type tours in english (I
have found this especially true in Germany and Scendinavia).

Under the category of 'other suggestions' - if you are planning for next
summer - you could make dokumenta in Kassel, the Venice Biennale, and the
opening of the Guggenheim Bilbao (Spain) all scheduled to open within a few
days of each other.  There are obviously many museums enroute:  Kassel has
the only wall paper museum in the world and The Museum of Sepulchre
Culture.  Madrid has the Prado, the Renia Sophia and the Thyssen Bornemisza
(sp?).  Venice has lots to see....

Suzanne Quigley
Guggenheim