Among friends and family, it's mainly 2× yes. You see a lot of banners in the cities for the initiative, but I don't know how good an indicator that is (political banners seem to have boomed in the last 3 years: each campaign now has its own that people rush to hang on their balconies, etc). As you said, in the countryside, you almost only ever see the 2× no ads.

I don't really know how to probe for the general sentiment: you can look at what the different political parties recommend on their websites (that's my usual lazy voting strategy: if the green, socialists and far left agree on a choice, I'll usually go with it), look for polls and/or read the press (probably swissinfo.ch is a good starting point?). Typically in this case, the socialists and green agree on the 2×yes, and since the socialists are pretty tame, I guess it's a good indicator that I can safely vote that.

EDIT: Correction, the tendency among my entourage might be tilting to a "no" to the drinking water initiative!

Why the downvotes?