Well, if you take the cities of Coral Springs (121,000), Margate (53,000), Tamarac (60,000), Coconut Creek (53,000), and Parkland (24,000) which use "Pompano Beach" (100,000) as the postal mailing address, you get around 410,000 folks, not including a few thousand that live in unincorporated areas between the city limits. Boca Raton kind of tilts the scales, since roughly two-thirds of the "postal boundaries" of Boca Raton are technically unincorporated; plus the great number of people who work within its actual city boundaries probably distorts a lot of information (since many people are likely to go out to eat when on the job).
But that Dallas number is absolutely staggering; I didn't notice a lack of supermarkets when I was in the DFW area.