possible fix to ios6 wifi issue
Here is a possible fix. It is working, for now anyway. Regardless, Apple need to sort this out.
1) Add/remove your home network a few times
2) Toggle and try with Ask to join: Yes
If no sucess,
3) Remove/add network again and select No
Restarting phone between toggling seems to help.
Hope this helps.
iPhone 4, iOS 6