I say write your DJ in whatever language you feel more comfortable with or a mix of the two depending on your mood for the day. As long as it's not confusing you then I don't think it will affect your dreams in a negative way at all if you decide to switch it up. I do think whichever language you use/hear more during the day and even in your internal monologue will be more prevalent in your dreams, but that shouldn't be an issue. I wish I knew another language well enough to have an experience like that.