If you need lengthy instructions to show someone how to use your UI, you should reconsider your UI.
http://www.jnd.org/dn.mss/are_the_new_elevators_bad_design.h...
You are right that there's an initial curve, though, and I don't know how to deal with that other than just through the painful experience you described.
If this was a deadly choice, between an elevator and a trash compactor, it might make sense to over-sign it. As is, it's a trivial and obvious mistake, especially if each bank has a sign saying 'Floors 1-x are reached via the other elevator bank' for someone to read on their round-trip.
Part of the reason users are so clueless is because we go too far in padding their environment. People don't slice off fingers because the sharp end of the knife wasn't properly labelled - they exercise caution.
Then they retrofitted a similar system back at my corp HQ. It had you enter your floor on a screen on the wall right in the middle of the elevator lobby and it was (and is) kind of a pain in the ass...because when there's a crush of people waiting for the elevators, you can't get to the screen to enter your floor. When it was just the "up" and "down" buttons in the same location, the odds were pretty good that someone in the crush had already pushed the button you need, but...
I don't think owners of office buildings realize how painful it is to have slow elevators. We moved our office out of a 30 story building with 4 elevators, because the unbearable wait to get in and out of the building during peak times.