[Alan Anderson]

I think the easiest way to make it work is to add a pullup resistor (10k or so) from signal to +5 volts, and connect the switch from signal to ground. You'll read 5v when the switch is off, and 0v when the switch is on.

You could even use a half dozen or so resistors to make a rudimentary D-to-A conversion circuit, which would let you connect all three of your switches to a single analog input, but that's probably a bit fancier than you need to get.