Multiple arduino's reading the same digital input?

basically I need to setup many arduino's (60+) to read the same digital input. Now each arduino will be powered by a separate power source, And be a few meters apart. I was originally going to network them with RS485. But that was too complicated to achieve a simple task. Basically I will have one "Master" arduino and all of the rest will be "slaves" in a networking sense, Because of the distance I am thinking I'll have to use a higher voltage as my signal (12VDC or 24VDC) and use transistors to reduce it to 0-5v input which will come from that local arduino's power supply. The main goal here is to control many 20W RGB LED's that are spread across hundreds of meters.
Is this possible?, or is there a better way to do it?

So the plan is to have one Arduino use PWM and an RC filter to generate an analog voltage to be read on 60 other Arduinos?

All that and stepping the voltage up and down sounds fraught with problems. Noise, line resistance, etc. You don't need to network them. Just have one broadcast the number from as an RS485 signal, and the rest just listen. It doesn't sound like there is any reason to have them talk back.

Comm's will just be one way, master to slaves?
Connect Tx/Gnd from Master to Rx/Gnd of all slaves. If you don't want to do RS485, then RS232 from master out to all slaves.
Analog input to Master only, send out whatever level the slaves are to provide via PWM or whatever.

Whatever goes in to the Master, sending out to the slaves will be the same.

If the slaves are individually powered and you are concerned about getting a common ground from all the slaves back to the master, then you can optoisolate the signal at the slave end instead -

CrossRoads:
Comm's will just be one way, master to slaves?
Connect Tx/Gnd from Master to Rx/Gnd of all slaves. If you don't want to do RS485, then RS232 from master out to all slaves.
Analog input to Master only, send out whatever level the slaves are to provide via PWM or whatever.

thank you. Using the RX/TX pins to communicate might be the way to go, even as you say if I'm not recieving and just sending it will work. I'm just concerned about the distance I can send a serial signal. From what I've read the 0-5v serial signal is lost after ~15 feet or so without using a RS485 or 232 chip, which I was trying to avoid because my circuit boards are ready to be etched and the parts to make all 60 boards have been ordered. It would be easy for me to add an input with what I have so I thought about going the other route I was talking about earlier. I did at least add in RX, TX and COM connections on the boards, But dimming the LED's was added in last minute as my circuit is meant to serve a different purpose (shut off the LED in case of overheat and cooling fan failure) but that other control needs to be there now.

just use a gigh input impedence buffer, you can get digital buffer IC's or a non inverting opamp with a gain of 1 will do it.

Infact as it is digital just use a mosfet like a 2N7000 with very high gate impedance you can put any number in parallel close to each input. Might be worth having a current boost buffer (another transistor maybe power like IRL540N) on the output of the master, job done.

"From what I've read the 0-5v serial signal is lost after ~15 feet or so without using a RS485 or 232 chip"
Nonsense. The 328P has pretty high level drive capability. The problem is you are going to a lot of cables over much longer distances.
For 60+ receivers and hundreds of meters of cables, you really need a driver.
MAX487 is designed for situations like this. 8-pin part and space for a resistor is all that's needed. See page 13/14 of the datasheet.
http://www.digikey.com/product-search/en?vendor=0&keywords=max487