Like a few other folks mentioned... to get to the Disney Boardwalk from any Disney resort... take a bus to one of the parks, and switch to the Boardwalk bus. HOWEVER... I have a few additional peices of advice...
Don't use Epcot as the hub... the busses drop you off in front, but then you'd need to go into the park, walk allllll the way to the back, and then take the boat... (or walk further).
My recommendation is that you take the bus to the Disney/MGM Studios, and from there catch the Boat to the Boardwalk... The boat is right near the bus load zones. This way, you get a nice picturesque boat ride of the Epcot Resort area... a very pretty area at night. Be aware though... these boats don't have horsepower... they have snailpower... lol... They're also very cool in the fact that they don't have forward/reverse... but rather, the propeller can rotate 360 degrees. (which is how they make some of the tight turns)
This method will be effective up until 30 mins prior to the Studios close time. After that time, I'd recommend going to Downtown Disney, and switching busses there. (The reason being at that time, the boats start to get crowded during the park exit)
For getting back to your resort from the Boardwalk... catch the Downtown Disney bus, and then switch there.
One side note... At this present time (and subject to change)... Coronado Springs will SOMETIMES have a bus that goes directly to the Boardwalk... thier Downtown Disney bus goes from Downtown Disney to Coronado Springs, to Boardwalk, and then back to Downtown Disney. However, this additional stop is only during certain parts of the day. Check with the driver to be sure.