SimCity isn't coming until March 5, so you'll have to wait for the flowers to bud before you can start your urban layouts. But you might get your chance to play a snippet of the game as early as next weekend, when the beta kicks off.
You can register for the beta now. According to an SimCity's Twitter, the beta will start next Friday, January 25, and last through Monday, January 28. It will feature a "one hour slice" of the game, but the announcement isn't clear on just how many eager city planners will get in on this round of beta invites. March is still quite a while away, though, so it seems likely we'll see more waves coming leading up to launch.