while what Jan suggest "outputs tied to individual LEDs plus series resistors to limit current to LEDs" is, indeed, doable. However, the thing you most likely will see is that the LEDs will be a bit dimmer when many are lit, than when only a few are on. Of course a bombastic power supply and heavy gauge wires will take care of that, but using constant current chips, as I suggest, allow your power to sag a bit which makes many things much simpler. Another benefit is that you will not need a zillion current limiting resistors. The cost of a CC chip is not much more than the cost of a 'standard' chip and resistors.

Erik

PS do not forget to buy matched LEDs, your sign will look so much better.