If You Build it, Will They Come?
Before you choose a location, you need to take a look at the type of people that live nearby. While you may have a gut feeling about a particular area, it's smart to actually look at the numbers.
While CrossFitters come in all shapes in sizes, the 'average' CrossFit customer is white, between 25 and 34 years old, and has an income over $150,000 per year. That's a pretty narrow demographic you need to find, and of those, income is probably the most important. Compared to a normal, big-box gym, CrossFit is expensive, so you need customers that can afford it.
You can use a site called FreeDemographics to find information about people living within a defined area. While the information on that site is based on distance between where people live and a target point, you also need to consider travel time. People may drive 20 minutes to get to your box, but will they drive 30 minutes? MaxWod has a good overview on how to use FreeDemographics for find demographics for an area..