When to use the words 'good' and 'well'?

I have to write a paper about Helen Keller, and I don't know which word to use. I know to use 'good' as an adjective and 'well' as an adverb, but which word would fit in this sentence? "Although her speech wasn't very understandable, it was ______ enough for Helen to go to college." Help?! :):):):):):):):):):):)