Both streets are lined on both sides with bars. I have seen as much partying outside on the streets as I have seen inside the various bars. I've enjoyed a few beers at a couple of them (and that's all).
Not all bars and clubs are on these two "hills." I have seen many throughout Itaewon. Also, I've seen many (and have eaten at a few) restaurants featuring international cuisines.
Besides eating some lunch, all I did in Itaewan was walk around. That required only a couple hours of slow walking.
I've eaten western styled breakfast at "All American Diner" a few times. Pricey, but delicious!