You might want to look into the magnetic water conditioners. I personally don't know anything about them, but they sound interesting and more desireable that a conventional softener, if they work well.
Here's a link with some info.
I can't answer about the effluent on the yard. Overtime, it's bound to be at least somewhat undesireable. We had a water softener when I was a kid and it drained into the septic system, but we were on a aerobic septic and it went into the leach fields. Actually it probably wasn't as often as every month, since my dad was notoriously bad about forgetting to refill the water softener.