That will probably work best. Otherwise just try using a regular guitar cable with one of those headphone jack-sized adapters attached to one end.
I'll be returning my Lightsnake soon. HORRIBLE sound quality, tons of latency issues, and a loose connection. The thing was broken the minute I got it. I've heard this is a pretty common issue. STAY AWAY!
What is different about the audio input port on a Macbook vs. a Macbook Pro that would cause this? As far as I can tell on the Apple tech spec pages, the audio inputs are the same. Please enlighten me. I am looking to play my guitar through my MB (not MBP) and would like to know what I need to get....Also, if you have a Macbook, iBook, iMac (or basically any of the non-pro computers) you'll need the Griffin iMic (adds an audio-in jack using an available USB slot). That can be found here: http://www.griffintechnology.com/products/imic/ or you can find them for about 10 bucks cheaper on eBay.
edit: nevermind about the iMic. You have a Macbook Pro. You're good to as far as the audio-in is concerned.