I need some recommendations for an inexpensive guitar-to-USB interface that will work well with Sonar X2 Studio. I'm a complete newbie when it comes to recording so any help will be greatly appreciated.
 
Thanks,
Charles

Welcome to the forum.
I'm glad you haven't bought anything, yet. Those guitar-to-USB things work okay... as long as you don't mind not hearing yourself playing in time to the tracks you've already recorded. They don't synch up well with whatever other sound card/audio interface you are using.
You should save a few more bucks (I know you said "inexpensive") and get an audio interface designed for recording that you can plug a guitar, microphone or other instrument into. The savings on headache pills you won't be buying will justify the added initial cost.
What equipment do you already have?

Take a look at one of the smaller USB audio interfaces from Focusrite (ex. Scarlett 2i2), Presonus (ex. AudioBox VSL22) or Roland (ex. Duo-Capture EX).

I'm no expert myself, those USB interfaces look good - I got a Samson gtrack, it is a nice mic and also has headphone port and 1 instrument port (for guitar).  I've meddled with it a bit and get some great sound from it! I've also ordered Samson graphite 49 key controller... can't wait for it and should arrive this week..

As Greg pointed out the midi guitar things don't work well, nor do the USB mics when you really want to do serious recording and multitrack recording.   Basically you end up trying to use 2 sound cards and since they are not synced to each others clocks, you have tracks that drift out of sync as the song progresses even though they seemed to be synced while recording.
 
The solution is to get a decent USB audio/midi interface as was suggested and do it right to start with.

I'll disagree with Herb and Gregg a little bit here, but they are giving you good advice.  I have (among a lot of other interfaces) a Behringer UCG102 Guitar-to-USB Interface that works well performance-wise on my laptop.  It provides for local monitoring and performs much better than the laptop's internal sound card.  I think I paid all of $35 for it.  Unfortunately, this is not the device you want.  You will eventually want to do more than one channel and work at a higher bit depth.
 
For all of $79 I think you can find an Alesis I/O 2 Express.  I think this is every bit as good a unit as any of the presonus, m-audio or other two channel interfaces.  It will take a high-Z input for your guitar as well as a mike after you decide you need to record something other then guitar.