The Purge is a terrible idea IRL, albeit a promising dystopian film idea.
No, I would not participate in The Purge. If my home nation (America) was doing this, I would relocate & apply for EU citizenship.
If it became global- I'd buy materials from various places, over an extended period of time, & build an underground shelter, never telling a single soul. I would go there at least a month before The Purge. Perhaps even lie to those familiar with me, & tell them I took it as an annual vacation, one I liked to finish out by losing my shit on some poor indigenous person in a far-off land before returning home. Maybe add some classic NF bs about how it makes me feel reborn or something, to make it more believable.
It would be like Christmas - everyone would spend all year thinking about it and then preparing for it. Legalised murder would not lead to wanton violence so most people would be unaffected. On a side note: how would they prove someone was killed during the purge and not shortly before or after it?
As for me I would spend all year determining the sensing types in my area and when it begins try and slaughter as many as I can. Perhaps set up a Facebook group so teams of N's can be better organised.