Yes, just drive through the park, through zone 3 and over the wooden bridge and you'll see the confluence of the spring and the river.. It's most definitely wadeable.. I'd suggest driving past the wooden bridge, and out to 64. Turn left and go over the main bridge and you'll see the public access parking on the right.. That access goes back around 1000 yards and has 3 or 4 points where you can wade in...
But don't venture too far downstream, certainly don't go below the island.. There's no fish down there..