Yes we stayed at the City Park a few weeks ago.
When you get to the park you'll see a sign pointing to RV camping. It's one road and the back end was taped off. No marked sites, just find a spot. I suggest you find a spot with your RV pointed out since the placed filled up by morning, we had to back out 100 feet to get out of there. There is a turn around at the end of the road.
The park in nice, mostly shaded, right on the river (mostly dry right now) and there are some good walks over a foot bridge. The actual park is adjacent.
Not perfect but it's free.