You can find it here (on a pod-cast, mp3)
http://www.booksshouldbefree.com/book/the-importance-of-being-earnest-by-oscar-wilde
Here it is from Project Gutenburg:
http://www.gutenberg.org/ebooks/26226
Here's the PDF version I'll be using in class
http://www2.hn.psu.edu/faculty/jmanis/oscar-wilde/importance-of-being-earnest.pdf
Here's the Spanish edition in pdf
Audio in Spanish