OSX won't automatically connect to WiFi
Solution 1:
Reading this question reminded me that I had dealt with the same problem with my Mac awhile ago.
I fixed it by writing a shell script which was automatically called via launchd
whenever /Library/Preferences/SystemConfiguration/
changes.
You'll have to configure a few things, mainly create a list of known SSIDs and passwords for the networks that you join.
You can find it here: https://github.com/tjluoma/airport-autojoin
Solution 2:
Sometimes network locations get messed up, but you can start fresh: go into the Location menu and create a new network location. Click on Apply, and check again and the WiFi situation improves.