Hi Bryan!
Welcome to planDisney.
I'm happy to hear you'll be staying at
Disney's BoardWalk Inn. It's in such a lovely location on Crescent Lake, with all that
Disney's BoardWalk offers in the way of dining and entertainment, and you'll also be within easy walking distance of Disney's Yacht Club and Disney's Beach Club Resorts, EPCOT and the
Disney Skyliner. There's a slighter longer walk to Disney's Hollywood Studios, but you can also use the Skyliner to get there.
The only way you can walk to the monorail is by having a park admission ticket for EPCOT which will allow you to enter through the International Gateway and walk to the front entrance of the park, where the monorail is stationed. I would not recommend that you do this as it would be a total waste of a day's park admission.
If you want to arrive at Magic Kingdom by monorail, there is no easy method of Disney Transport to take you to the monorail but you could book a Lyft rideshare to the Transportation and Ticket Center (TTC) from where you'll board the Express Monorail around to Magic Kingdom Park. The TTC is also where the parking lot for Magic Kingdom is located. If you download the Lyft app to your phone you can see the various vehicles available, and the different price ranges. I have used them many times and found them to be efficient, reliable, and reasonably inexpensive.
The most direct route for you to arrive at Magic Kingdom would be by taking a
Disney Bus from your hotel. All Disney transport begins operating around 45 minutes prior to park opening times (at least 7.45am for Resort guests' early entry at 8.30am, but I recommend you wait at the bus stops by no later than 7.15am to ensure you can board one of the first buses). I know that this completely bypasses the use of the monorail, so may not be a useful idea for you, but it would be quickest.
Please come back and visit us if you have any further questions, and you can
send me a direct question if you wish. We are always happy to help you plan your magical vacation to Walt Disney World!
Sue