I frequently use the monorail with my scooter, and I can say that it has gotten MUCH better in the last year or so. Probably won't be necessary, but it does always help, though, to be aware and have a member of your party on the lookout for a monorail CM to flag down for a ramp. Whatever you do, however, don't grab one yourself from the stand! Just have somebody in your party stand there obstructing the doorway till somebody comes to get you, LOL. 90 times out of 100, though, a CM will be there or at the car next to you. The worst place I've found is the TTC returning from MK, where you would switch to the Epcot monorail, or go to the MK parking lot. Everywhere else is excellent, and greatly improved from a few years ago.
Just to let you know, however, when you get into the car you go in facing forward, no problem. Therefore, getting off, you back off, and that's where you may find a bit of difficulty. If you (or whoever is using the scooter) has never driven one on ramps before, you may want to keep this one thing in mind and be aware of it, or maybe let somebody else back it off. But when you do back it off down the ramp, just as you start to back down, there is about a two second "oh no" moment where it feels like you are backing into thin air! You aren't of course, but it feels like it. My DH didn't understand why every time I backed off I had a moment where I just froze for a second until I made him do it once - you should have seen the look of pure fear on his face!
After that, its just a straight shot down the ramp, but if a member of your party can stand at the end of the ramp to kind of block the stampeding horde getting off the other parts of the monorail while the person on the scooter gets it going forward again, that would be helpful. Over the years, my family has gotten very good at known when and how to form a phalanx around me and the scooter or wheelchair - we probably look like a Roman army at times, especially after Illuminations, LOL!