As the proud owner of a number of pawn shop guitars, I think you can get a decent beginner guitar, and occasionally a mid-range guitar, but, in my experience, you're probably not going to find a really nice guitar in a pawn shop. The reason is that the person that owns a Les Paul can sell it for a lot more than he can pawn it for. You might have better luck in a specialty used guitar shop, but the price is not likely to be incredibly lower than a new one.

You can get a good used guitar, but you should check it over really well before you take it home. Make sure the frets are in good shape, the neck is straight, all the electronics are in working order, etc. Once you walk out of the shop with it, any problems you have with it are yours.