PTMGR
To change the default language on your dump.bin firmware file after extracting it, you will need to use
Firmware modifier which can be downloaded
here.
Download it, open it, select your firmware file then down the bottom there is a section called "Default Lanugage". Change this then press [OK]. It will then save it to the dump.bin firmware file. You only need to do this ONCE on that file and it should be like that all the time.
From then onwards, any other updates with that same dump.bin file should always default your language to English.
Hope that helps.