nRF24l01+ Outputting Garbage Values
Check these things first:

Is your power supply give a constant 3.3V and a minimum of 0.5A(500mA)?
Does your code work for others?
Are you on the right serial baud rate?
Is the path from the radio to the Arduino as short as possible?
Are your MISO and MOSI wires twined into each other?

If none of these things help then, please tell me what library you are using. I had a lot of issues with the RF24 library so maybe try using the NRFLite library.