I don't want to go when he is not there. OR: I want to go when he is not there; I don't want to go when he is there.
Comment:
The utterance cited here was produced in a context where negation clearly had scope over both the main proposition and the embedded proposition. Elicited judgements and spontaneous production both confirm that the utterance also has the other translations provided here, where negation has scope only over the embedded proposition, or over the main one.