If someone you know has told you that it is wrong, you should politely challenge that person to substantiate such a claim. So long as the Latin Mass you attend is either a standard Roman rite Mass done in the Latin language or is a diocesan-approved Tridentine Latin Mass, there is nothing wrong with attending a vernacular-language Mass during the week and a Latin Mass on Sundays. So long as both parishes are in union with their respective local diocese, this is true even if you must attend different parishes to do so.
