I am planning to backpack the Jordan valley loop on the Friday before Memorial day. I am really paranoid about whether there will be sites available. How busy does it get?
EDIT: We left late and didn't get to the campground until 7 pm, but there were tons of open spots! There were a lot of gnats, though.
It's not a car camping place so I don't think you'd have a problem finding an open site Friday. If the numbered sites do happen to be full, there's overflow camping allowed in the field in the middle so you will still have a place to set up.
I used to go for day hikes there all the time when visiting my grandparents nearby. Between Pinney Bridge and Jordan River Rd is my favorite stretch. Stop by the fish hatchery if you have time.