If you download a "Option File" from forums like PESEdit or PES-Patch, these names are usually already corrected. However, for vanilla PS3/Xbox 360 players, you must do this manually.
(Note: England surprisingly kept most of their real names, but stats were often underrated. Look for —sometimes faked as "Beck.") pes 2013 classic players real names
Here is your definitive guide to the real identities behind the fake names in PES 2013. If you download a "Option File" from forums