Entrepreneur Magazine has teamed with business information specialists Dun & Bradstreet to provide a ranking of the nation's best cities for entrepreneurs.The two cities tied for the top berth are Dallas, noted for a well-trained labor force, strong city leadership, and an extensive transportation network, and Orlando, seen as a high-tech hub with a reasonable cost of living and an attractive climate.Other cities filling out the top five include West Palm Beach/Boca Raton, Florida, Washington, D.C., and Austin