I will noramlly put everything in my glutes (except snythol shots ofcourse) I personally think that circulation is just better overall threw your glutes when you put your gear there...I dont know for sure, but it seems like it (probably just in my head..LOL)...
As for using pain killers, I would just use otc stuff before doing the harsher stuff like vicoden, or aleast try tramadol out (its not a narcotic, but has alot of the same effects, might be a tad healthier than other stuff)...things like vicoden or Oxyc. are very addicting and if you have a addicting personality than that might be a bad thing...I remember being in FL and doing GHB everyday for half a year, straight...I felt like I couldnt function without it...LOL !!! But no really try OTC stuff first (Ibeprofen, ect)