Re: unable to load city at this time. Please try again later

Try this:

1. Log out of SimCity and Origin.
2. Navigate to your SimCity game folder; the default location is C:\Program Files (x86)\Origin Games\SimCity\
3. Delete the SimCityUserData folder (don't worry, the game will recreate it when you log in). 
4. Set your SimCity and Origin shortcuts to "Run As Administrator" (right-click the shortcut, choose Properties, Compatibility tab, check box "Run As Administrator"
5. Run SimCity again

If this doesn't work, please start a new thread and let us know whether you're running on PC or Mac, your OS version, and any error messages you get. Good luck!