I think I read on some forum somewhere that Frenzy could have uploaded information to Megatron while he was messing around with computer systems, allowing him to speak english right away. Granted that is just a possible theory from a fan, but it's a pretty good explination. Since we already found out that the Autobots learned english from the WWW, they probably figured it would be redundent to explain how Megatron learned as well. Also there isn't much development of the Decepticons in the movie, there isn't much need to throw that little tid bit in.
But yeah, awsome movie.
I was aware of the fact that if they didn't do a good job, there would be a lot of pissed off Transformers fans, but I'm glad that wasn't the case.
