"God wrote two books: the first is the bible* and the second is the book
nature, which allows humans to observe and experience nature and to answer
questions about the universe."
The letter she is thinking of can only be his Letter to the Grand Duchess
Christina (de Medici), dowager duchess of Tuscany and mother of his patron
Cosimo II. It is found in a generally (not always) reliable translation in
Stillman Drake, Discoveries and Opinions of Galileo (Anchor, 1957 and still
available). There is no quotation like this there (as far as I can find),
but Galileo says many things overlapping with this. The closest (not that
close) is on page 183, where he actually quotes Tertullian: "We conclude
that God is known first through Nature, and then again, more particularly,
by doctrine; by Nature in His works, and by doctrine in His revealed word."
Much better, IMO, would be to use the pithy little statement that Galileo
borrowed from his friend, Cardinal Baronio: (p. 186) "That the intention of
the Holy Ghost is to teach us how one goes to heaven, not how heaven goes."
The whole YEC movement would do very well to read this letter in an
attitude of honest searching.
Another comment. I have not meant to suggest that anyone write a statement
for the ASA officially, though perhaps this could take place. What I meant
was for several ASAers to agree on what an appropriate statement would look
like, and for them to send this as individuals to Dr. Dobson. Better yet,
if some of us could meet with him or appear on his program. I've contacted
persons in his organization about this and have had no reply thus far.