I would definitely leave it in the off position.
Next time you take it to your tech, have him disable it, then you won't have to remember. The problem is not with the switch, since you have a ground on your cord, but rather with the capacitor that leads from your switch to the chassis of the amp. If this capacitor fails and starts conducting, you will have 120 volts on the chassis of the amp, which means that it will lead straight up your guitar cord to your strings. This electricity should have no place to go, in theory, but when you touch something else, you will get a nasty surprise.
I've had the sh!t shocked out of me quite a few times at gigs in places with no ground, it is really dangerous. Plus it hurts like a *****.
When I lived on Maui, we played a lot of gigs in people's yards, just a few feet from their pools. While we were out of the way of the splashing, we were still close enough to be standing in water.