Just got back. Here's the skinny on the monorail. As others have mentioned, there are two stations; one outside
Disneyland and one inside.
The one outside is in downtown disney, about 8 minutes walking distance from the park entrances, and about 2 minutes from the disneyland hotel. The one inside is at tomorrowland.
All passengers must get off at the tomorrowland station. That means if you board in downtown disney, you may only go to the next stop, which is inside disneyland. If you board at the tomorrowland station in disneyland, you can either get off at downtown disney or continue on for the complete loop. But you cannot stay on at tomorrowland station.
The entrance to downtown disney has a park entrance pass reader. In other words, it serves as an entrance to disneyland. So if you get on the monorail there, your ticket will be scanned and you will lose one day. If you leave the park there, you can get your hand stamped to reenter. In essence, it's the same as the regular park entrance. Since the monorail goes directly into the park, the first ride usually does not leave downtown disney until the park has already been open for at least a few minutes. So, for example, when we were there, the official park entrance time was 10:00 a.m. The main gate opened around 9:45, and the first monorail left downtown disney around 10:05.
Starting about 30 minutes before the park closes, you can no longer do a complete loop from the tomorrowland station. You must get off at downtown disney and leave the park.
Hotel guests do get some special privileges. If you show your key or your charge receipt, you can get in a special line at tomorrowland station and bypass the regular line. The primary utility of this is if you want to take the monorail back to downtown disney at park closing, when everyone is trying to get on.
Starting in downtown disney, the route takes you around the west side of the park (you don't see much) and into tomorrowland. You do a couple of loops around tomorrowland, mostly over a proposed new attraction (which looks a lot like the old 20,000 leagues under the sea from Florida) and over autopia and then into the station. From there, you go around the east side of the park, and again don't see much of the park, through the GC hotel, and into downtown disney station.
