well, let me give it a try.....
Let's start with the orientation of your map- my directions assume that you have the map laying flat on a table with the front lobby side of the YC/BC closest to you.
As far as a general orientation goes. Epcot is a short 3-5 minute walk from YC/BC. This takes you to the International Gate of the park. It is just out the side door of some BC rooms, or you simply walk out the back lobby doors of either YC or BC turn left (just before you walk into the water -of the lagoon that makes the "water view") and follow the path "straight" on over to Epcot. Now as you top a hill on this path you come to a fork in the road (and as Yogi Berra would say... when you come to a fork in the road - take it) - my children refer to this as the "low road" or "high road" option. The "low road" ends up at the same place as the "high road". The "low road" simply takes you closer to the canal. The "high road" goes down a hill and meets back up with the "low road". Both "low" & "high" end up just outside the International Gate at the loading/unloading area of the boats that travel between Epcot, the Epcot Resort hotels (YC/BC, BW, Swan, & Dolphin) and MGM.
Now back at the "fork in the road"... there was a turn that you could've made- a right turn across a bridge that would take you over to the Boardwalk and Boardwalk Resort. If you follow this path over to the Boardwalk you will see ESPN Club, which is the "Epcot Side Anchor of the Boardwalk" - what I mean is that ESPN is the first building you pass when walking from Epcot onto the Boardwalk. If you continue along the path, eventually you will come to the "center" of the Boardwalk area. Stop! If you look straight ahead you may be able to see the Swan & Dolphin hotels, more than likely you will see the Atlantic Dance Club, which is at the end of the Boardwalk. Look left, you will see the Boardwalk Resort (and what a sight it is- huge staircase leading up to the lobby, beautiful lawn area) Look right (or behind you if you are still gawking at the Boardwalk resort), you will see the boat loading/unloading area look farther across the lagoon, you will see the YC/BC - YC will be on the left -it is grey in color and the BC will be on the right - it is blue in color. You will also see the "shipwreck" that makes Stormalong Bay's waterslide. If you keep walking along the Boardwalk past the shops & restaurants you will get to the "MGM Side Anchor of the Boardwalk" (first building when walking from MGM)- Jelly Rolls (some may argue that it is Atlantic Dance Club, I won't quibble).
Now for MGM. MGM is about a 12-15 minute walk from YC/BC. You may also take a boat, which is directly out the YC lobby and out the BC lobby and a right turn to the boat dock. The boats first stop at the Swan & Dolphin hotels (which are on the right side of the YC and closest to the YC, they are also on the right of the BC - but farther away). After the stop, the boats wander down the canal and stop at the dock just outside MGM- the boat ride takes about 20-22 minutes.
Now assume you are walking from YC/BC. Let's take a quick break and re-orient from the YC/BC side. Walk out the back door of either lobby (YC or BC), just before you walk into the water - STOP in the middle of the path - look straight ahead you will see the Boardwalk area and the Boardwalk resort, look left and you will see the Epcot area, probably France as the Eifell Tower is most visible in this area, look right and you will see the Swan & Dolphin hotels.
Back to our walk over to MGM from the YC/BC.... as you walk out the back of either lobby turn right on the path (it is actually a boardwalk, but I didn't want to confuse you - unless I already have). Follow the path around behind the YC/BC resorts, it eventually ends (it also becomes a sidewalk in lieu of a boardwalk) at a place where you must decide (go straight, turn right or turn left), you choose and turn left (as an aside if you walk straight you would eventually end up at the Dolphin, assuming you follow the path, if you don't follow the path you get wet because you have just walked in to the lagoon/canal, if you turn right instead of left you are walking around to the front of the YC via the parking lot area) - back to our decision LEFT turn and across the "Dolphin Bridge". You are now walking toward the Boardwalk, the Swan & Dolphin are on your right and the YC/BC are behind you. At the bottom of the hill (after you cross the bridge), you are faced with yet another decision, straight, left or right? If you turn right you would walk across the "Swan Bridge" and would be heading dircetly toward the Swan hotel. If you walk straight, you would be walking into some of that lush green WDW grass, some of the same lush green grass that we saw in front of the Boardwalk resort (you would eventually end up at the same place we are trying to get to) - but let's "KEEP OFF THE GRASS" - it looks so nice. So turn left - you are now on the other end (from the Epcot description) of the Boardwalk (it is a boardwalk too). Another quick right turn will put you on the pathway to MGM (I think there is even a little sign to that effect). You walk along the canal, pass the Boardwalk Resort (which will be on your left as you are walking), past the Boardwalk resort pool area and tennis courts, walk a little further and you are under a bridge, a slight turn by the path back to the right and directly in front of you will be MGM. Now as you are facing MGM in this location, the Boardwalk, Boardwalk resort, Epcot and the YC/BC are behind you - the Swan & Dolphin are on your right and slightly in front and MGM is of course, is in front of you. Follow the path, it will appear as if you are walking into MGM's parking lot (and you are by the way) - stay on the path - watch for cars & buses- follow the path and eventually your instincts will take over as you see the gates of MGM. You will break into first, a fast walk, then a jog and finally into a full sprint - until you hit the line waiting to have their bags checked (thank you Osama, for taking an extra 15 minutes out of my MGM time). In any event, you have made it!
As far as the Water View - the rooms face the lagoon that wraps around the Boardwalk (which is directly across from YC / BC) then there are canals that wind their way over to Epcot (on the left) and the Swan and Dolphin hotels (on the right) and then finally they wind their way on down to MGM. In my oipinion, the water views are nice, I believe most have balconies. If you are lucky, you can get a "double water view", one of the lagon as well as Stormalong Bay. We have stayed in a water view a few times, I'm not certain that the "view" actually warrants the upgrade cost.
As for the fireworks view. The rooms that might have the view at BC are going to be on the left side of the hotel. These rooms are somewhat obstructed (at least the ones we have stayed in) by a woodsy area that seperates Epcot from the resort. We have not stayed in a YC water view before, but it seems to me that YC rooms that face the BC and Stormalong Bay would have great views of Illuminations.
Now that you are completly and totally confused - don't worry about it - just print this out - take it with you and as soon as you can (once you are there) pull it out, follow the instructions and it will all make perfect sense. Have fun!!!