I just received this report from fellow river enthusiast Misha Collins, who kayaked down the L.A. River last weekend. I love it when people treat the L.A. River like a river:
Yesterday I put in by the 5-110 interchange and kayaked to Long Beach. I was in a 50 year-old wood framed vinyl kayak with a canoe paddle. I had to portage a total of about one mile (because I bottomed out), but would not have had to portage at all in a modern river kayak.
It was a little gross, but all in all much better than I expected. No run-ins with authorities, a few cheers from pedestrians, cyclists and taggers.
The last 10 miles or so were quite beautiful. Lots of birds and rushes and even big fish. I only capsized 4 times. I traversed one set of rapids on a floating mattress.
I put in around 2:15pm and got to Long Beach at 8pm. 26 miles Pretty Quick.
If you'd like to see the river up close yourself--but not quite that up close--you can sign up for bus and car-caravan tours on the Friends of the Los Angeles River website (full disclosure: I lead them). The next two are Sunday 9/9 and Sunday 10/7.