Just picked up my first BMW a couple of days ago!

It's an '02 330Ci Sport + Premium package, and I _love_ it!
I live in California and am heading up to the mountains this weekend. The car has 17" Kumho Ecsta Supra 712 summer tires on it, which is pretty much all I need for most of the time. I don't go up to the mountains that often to warrant buying a separate set of snow tires.
I've read through the threads on snow tires here, and I've seen a few different recommendations, so I wanted to hear opinions from those of you who have driven with chains.
Here are my concerns:
The BMW driver's manual says put snow chains on the rear tires, except for certain tires, mine included (245/40Z17). The guys down at the auto parts store also confirmed that it's a bad idea to put chains on low profile tires.
If it does snow, they're likely to bring out the snow chain police, which means I won't be allowed to pass any road blocks unless I have chains on.
This weekend the weather is only calling for rain, and the tires are rated well for wet traction, so I'm keeping my fingers crossed that I won't get turned away this time. I'm planning on ordering some chains for the next time though.
The car has 60k miles on it, so I'm not covered under the 50k warranty anymore if that makes a difference. From what I read, BMW seems to be concerned about the damage to the rims from putting chains on, and they don't want to cover that under the complete warranty.
Anyone have any experience with "cable snow chains" on low profile tires? Will it do any damage to the rims? Can anyone recommend whether I should order the "ladder" pattern cable chain or the "Z" pattern?