This is an interesting, but curious question that seems to come up when people are looking at a career choice and when it comes to industrial design, there are certain places that will be better than others. Industrial Design is not like becoming a banker where there is a bank in every little town in the world. It is also not like becoming a stock brocker where there are only a few centers of finance where you can have an effective career such as New York, Toyko, London and Paris. The good news is that Industrial Design is practiced in many of the great cities of the world!
Design happens in every major industrial city and many non industrial ones. You would be far better to look at what type of design do you want to practice and what type of products interest you. It is not so much which cities, but which companies would you like to work with or for and then comes the question, where are their design departments based? Design consultancies tend to be clustered in a few large cities and then spread throughout the USA. So look at San Francisco, Los Angeles, Boston, New York, Chicago, Detroit, Cincinnati as important centers for industrial design consulting.
IDSA has members all over the USA and many other places around the world in large cities and small towns, but in order to provide some sort of picture for you, here is a very simplified idea of Industrial Design in the USA today:
Automobile Design: Detroit (Ford, GM, Chrysler, Nissan, Toyota and others) and LA (BMW, Toyota, Nissan, KIA and others)
Aircraft Design: Seattle (Boeing), Montreal, Canada (Bombardier), Savannah (Lear Jet) and others
Space Craft: Arizona
Boat Design: Florida: Sarasota area and Miami and others
Bikes and other outdoor: Portland, San Francisco and others
Office Furniture: Grand Rapids, Michigan
Software: Seattle (Microsoft) and San Francisco (Apple, HP, Philips, Cisco and lots more…)
Medical Equipment: Boston, Seattle, LA, San Francisco
Housewares: across the US
Consumer soft goods: Cincinnati, Atlanta, Connecticut….many others (P&G, Johnson and Johnson, Kraft, Mars, Pepsico, Coca cola)
Electronics: San Francisco, LA (Samsung, Belkin), Chicago (Motorola)…others
Computers: LA, San Francisco, Austin Texas (Dell and Intel), and many smaller centers…
There are people who start consultancies in Salt Lake City, Sarasota and other less recognized "design centers" and they do work for companies all over the country and in most cases, the world. Geography is not a barrier to the design profession. This is an international profession where the best are sought out no matter where they are located.
However, there are a couple of cities that have bigger design populations and therefore many design businesses and therefore, perhaps, more employment opportunities than other cities such as San Francisco, LA, New York, Chicago, Boston, Detroit, Portland, Cincinnati and Austin.
Designers are explorers, they explore the unknown future of what technology could be and how it could be used to improve people's standard's of living. As such, they are generally open to move where the best opportunities present themselves to explore the future! Interesting jobs come in the most unusual of places. Stay open and willing to go where the opportunities are!