Be careful with this field. It was devastated by the Recession. Most planning agencies (both public and private) are funded by development. On the government side, this is through impact fees and development review costs. It's self evident how the private side is funded. Most agencies laid-off nearly half of their staff when the recession occurred, and it's been VERY slow growth afterwards. This has done a couple of things: 1.) increased the pool of urban planning applicants for each job out there, and 2.) created a horrible (in my opinion) trend of hiring entry-level, ill-equipped planners to fill the shoes of those who were laid off, just to save a buck.
I was in city planning for approx. four years, and fortunately weathered the Recession. I decided to relocate to an area where I could pursue a masters degree (not in planning which my undergrad is in). Sammie is right that most professionals in the field have their masters, and it's really the only way to climb the ladder. I was just very worried about the narrowness of the profession, so I'm getting my masters in something that will open a few more doors.