When They Must Leave Their Cars Behind, How Quickly Can People Learn to Enjoy a More Urban, Walkable Environment?

Answer:
Instantly.

Main Street USA - Walt Disney World, Orlando, FL

I visited Walt Disney World recently with my family, and was struck by the high design quality of the urban environment of Main Street USA, the park's primary gathering place. I was further struck by the fact that visitors to the park - many of whom no doubt come from highly suburban, auto-oriented environments - seemed to adapt to this urban environment seamlessly and were having a wonderful time!

Walt Disney World is designed specifically so that visitors must leave their cars behind. A massive parking lot intercepts those arriving by car. Visitors must then dramatically and memorably traverse the large Seven Seas Lagoon via ferry boat or monorail in order to reach the park itself:

Once arriving by transit at the ferry boat landing or the monorail station, the entrance to The Magic Kingdom is dramatically framed by arches under the picturesque station of the small replica train that encircles the perimeter of the park:

Once passing under the train station, one immediately enters a beautiful and well-shaped town square:

This square then leads to Main Street USA, which frames the iconic view of the focally-placed Cinderella's Castle in the distance:

Looking from Cinderella's Castle, a vista is framed of the beautiful train station back at the arrival end of Main Street USA:

This "theme park stage set" creation actually forms a strikingly effective urban spatial sequence: 

The fundamental details that are critical for walkable places are incorporated so convincingly that Allan Jacobs includes Disney's Main Street USA in his seminal book Great Streets.  (Jacobs documents the entrance to Disneyland in California, which is urbanistically virtually identical to the example in Walt Disney World in Florida):

Jacobs documents that Disney's Main Street USA:

• Is approximately 54 feet wide from building face to building face.
• Features 12 foot wide sidewalks.
• Has frequent doorways, one every 18 feet on average.
• Has an appearance of many buildings, one every 22 feet on average.
• Represents an idealized dream-memory of what made a great street, with stage set physical qualities that exist on the best streets: buildings lining the street, architectural details over which light constantly moves, transparency at ground level, pedestrian comfort, a hint of housing and habitation, a beginning and an ending.
• Is an example of how little area it takes to create a sense of urbanity.

As Walt Disney planned Disneyland and Disney World during the 1950s and 60s, he seemed to be painfully aware that the automobile, among other forces, was transforming the physical fabric of American towns and cities, often to detriment.  Main Street USA was inspired by Walt Disney's memories of his own hometown of Marceline, Missouri:

With additional stylistic influences from main streets in other regions of the United States, Main Street USA attempts to capture for posterity the character of a turn-of-the-century small American town.

Walt Disney said about his creation, "For those of us who remember the carefree time it recreates, Main Street will bring back happy memories. For younger visitors, it is an adventure in turning back the calendar to the days of their grandfather's youth." 

Thanks to Disney's Main Street USA, today over 17 million annual Walt Disney World visitors get to experience how enjoyable a more urban, walkable place designed around people (rather than just their cars) can be.  

Amazon: Great Streets (by Allan B. Jacobs)