Start right now. Consider whether you really want edp though. At top schools the chances of an edp acceptance are very low compared to lower schools. If you get rejected EDP, it puts you at a HUGE disadvantage versus other applicants since you will be receuving secondaries to other schools between 2 and 4 months later than most applicants.
I wanted to apply edp, but was discouraged for the above reason. Still got into that same school through the normal process, although it was more stressful.
Was it MiesVanDerMom who applied edp to her local state school?