If you own a vehicle listed as E85, yes you could run a full tank of it.
You can look here to see:
http://www.e85fuel.com/e85101/flexfuelvehicles.php
@Dudelive - Yes I agree, that's why I doubt I'll put more than 3 gal of E85 with 10 gal of the regular 87 stuff. Not to mention how corrosive E85 is on seals & stuff where regular gas has build in lube properties.
Find out where to get E85 in your area:
http://www.e85fuel.com/database/search.php