Here's a little more information to help actually answer your question without the noise. Sorry about the quality of the map. I didn't spend too much time getting it perfect. (I had to superimpose one up on top of another because you have measure two different distances at once.)
Images/Distances provided by Google Maps.
The red arrow is right out side of Earl of Sandwich in the Marketplace section of Disney Springs. That's the starting point for the distance measurement.
The top left corner of the map is the Congress Park bus stop at Disney's Saratoga Springs Resort and Spa. From there, you can hop on a Disney bus headed to Magic Kingdom. You'll make one additional stop at the resort before going to the theme park. Your final destination will be the bus loop just outside the entrance to Magic Kingdom.
Approximate Walking Distance: 2,200 feet (680 meters)
-----
The other option would be to head to the Disney Springs bus loop, which is located at the bottom left of the map. From there, you'd board a bus to Disney's Contemporary Resort. Upon arriving at the resort, you'd have to walk to Magic Kingdom (or go inside and take the mororail and stop three times).
Approximate Walking Distance: 2,400 ft (730 meters) at Disney Springs plus about 2,200 ft (700 meters) near Magic Kingdom = 4,600 feet (1,430 meters)
So, if you're in the Marketplace, the best option is to walk to the Congress Park station and go directly to Magic Kingdom.
-----
For the record, whether you are a Resort guest or not, you are not breaking ANY rules. From the Transportation - Frequently Asked Questions page of the Disney World website:
Q. I'm not staying at a Disney Resort hotel. Can I use the monorails, buses and boats to get around Walt Disney World Resort?
A. Yes. All Guests have complimentary access to our network of monorails, buses and boats.
Link:
https://disneyworld.disney.go.com/faq/transportation/public-complimentary-transportation/