Changing the ingame language

-go to the registry:

                               - type Windows key + R

                                -regedit

                                -go on HKEY_LOCAL_MACHINE -> SOFTWARE

Go on Wow6432Node for Windows 64bit and then Origin Games - >71402

Or directly Origin Games -> 71402 for windows 32 bit

After you will see a window on the right with  "Local                    "de_DE (german value)."   so double clic on Local and change the value to en_US

Now return to HKEY_LOCAL_MACHINE -> SOFTWARE and go on Bioware / Mass Effect 3 and look again on the right the "Local                    "de_DE" and change it to en_US.

If it doesn't work, download a the multi language pack files, copy all files in your Mass effect main directory and retry what I said for the registry.