The walk from MGM to Fantasia Mini-Golf is one of the few at WDW that I would say is doable. The distance as the crow flies is quite short, but the route you take walking is much longer, about 1 mile.
WALKING DIRECTIONS FROM MGM TO FANTASIA MINI-GOLF
To get there, first leave MGM and walk toward the lake. Go right when you get to the water, past the bus stops; this is the walkway that leads to the Epcot Resorts area.
MGM Entrance Map
The first major landmark you will come to is the bridge where Buena Vista Drive crosses over the canal and walking path. Go under the bridge, and on the other side you will see a path that will take you up onto the bridge itself; take this path.
Map of the bridge
You are now on a walking path that follows Buena Vista Drive. Continue on until you reach the first intersection, which is Epcot Resorts Blvd. Turn right. You will see Fantasia Mini-Golf accross the street, but don't cross yet, because there is no sidewalk on the Fantasia side.
Map of the intersection
Follow the path along Epcot Resorts Blvd. until you come to the far side of Fantasia Mini-Golf; during this walk, you will have the parking lot of the Swan hotel on your right.
Keep going until you have completely passed the Swan and Fantasia - there is a large crosswalk there that will take you safely across the road and lead you past the Swan and Dolphin's tennis courts to the Fantasia entrance.
Map of the crosswalk
DIRECTIONS FROM MGM TO CBR
As to getting from MGM to CBR - take the bus. It would be about a 2-3 mile walk, but there is a large section of Buena Vista Drive that has no sidewalk, and several intersections with no crosswalks, making it a very dangerous idea to try walking to CBR from ANYWHERE. Take the bus, and live to tour another day.