People should discount the Madrid experience really. Although none of the shitstorm was his fault at all there was a lot of bad feeling around from all quarters. Plus he only got a dozen or so games.
You're right, his English is good. The only thing is he has a bit of a sing-songy accent, a la Unai Emery (albeit better grammatically and so on). Some of his pronunciation is a bit off too, like that Spanish way of pronouncing "coach" as "co-atch". This may well raise the eyebrows of the more Little Englander set who will pretend that they can't understand him.
If near-perfect English with barely a hint of an accent is your bag, Roberto Martínez is the man