Galaxy S2 through USB won't connect to my Mac? I have an Android Evo, and it connects to my Mac just fine when connecting the USB cable. I can access the entire phone data. 

However, my wife's Samsung Galaxy 2's data can't be accessed on my Mac, even though the Mac recognizes the USB connection. How do I fix this?
If phone data/photos is all you're after, I suggest using Airdroid instead. No wires required, and will work on any computer.

If you're really set on using the cord, you may be missing GS2 drivers. You'll need to install Kies from Samsung.