Typical values of Glen flow law for glaciers?
For glaciology related doubts, the first place to look is The Physics of Glaciers by Kurt M. Cuffey, W. S. B. Paterson. Going through the section 3.4.5 Controls on Creep Parameter A, should give you a good insight on the topic. It also includes example values.    



As well as recommendations for values of A as a function of temperature.


This section is included in the preview of the book on Google books.