Picture sun-bleached boardwalks, pastel cottages, and kids on cruiser bikes with baskets. That’s Seaside, Florida, a walkable Gulf Coast community that nails the 1950s beach-town vibe in the best way.

Rental prices in Seaside are high, so I booked a condo about 2 miles east, in the area known as Seagrove. On our first morning in town, we rented bikes, which we used as a central mode of ...