ADDRESS
The address shown on my home page is for regular mail.
If you need to send something via a messenger service, you should use:

Centro de Radioastronomia
UNAM Campus Morelia
Antigua Carretera a Patzcuaro 8701
C.P. 58089
Morelia, Michoacan

PHONE

Phone problems are not uncommon here. (I note that the U.S. is rapidly catching up in this regard!)
If the number for "outside Mexico" (+52 443-322-2757) doesn't work, then you might also try +52 555-623-2757.
This will route your call through Mexico City instead of using the Morelia trunk.
Likewise for FAXes. If +52 443-322-2726 doesn't work, you might try +52 555-623-2726.