I'm planning on doing the same thing in a few weeks here(with an lm335 though). What did you do to waterproof the sensor?
I had nothing but trouble with the LM temperature sensors. I couldn't get stability regardless of the resistors I used. Averaging might work better for you than me, but I had enough and just gave up.
The one-wire sensors from Maxim are accurate and dead easy with the existing libraries.
Anyway, I've waterproofed one or the other a few different ways. The best I've come up with so far is putting the chip in a piece of heatshrink tubing, filing the tubing with silicone sealant, letting the sealant almost set, then heat shrinking the tubing to tighten it all up. It's the best compromise between waterproof and quick temperature response that I've had so far.