if you do NOT have a WiFi connection so the WiFi system is constantly scanning
I leave my wifi setting on all the time. I have set it to NOT notify me of open networks.
Merely turning off the notification should have no impact on your scanning, but that's my opinion based on empirical data.
As a general note, most custom ROMs have active scanning periods for the WiFi stretched further apart in a specific attempt to save battery life.
I like the idea of using locale to manage wifi BUT I think in the end if it uses GPS it will end up using more battery power than just leaving wifi on.
Nah, not for me. I like how it works stock. I have wifi right away every time. If it only scanned every 60 seconds, wouldn't that mean that 3G might get going for a minute until wifi got set up? That would end up using more power.
I say leave it on and don't worry about it.