Some instruments are actually very easy to learn; take it from a saxophone player. Once you know the basics on which key corresponds with which note, you're golden. Start with small basic songs, and you should find yourself getting a grasp on the instrument in no time.
While I only really have experience with the sax, I've heard that wind instruments are generally easy to work with.
The thing is that I would rather learn the guitar or piano, so I can sing as well. And I tried both, but I didn't have the discipline to practice, same with the clarinet in elementary school. My brother is the same way, he never uses his electric guitar.
However my singing is getting better not because of practice, but because of age. A woman's voice in particular peaks at around 30 years old in most cases and mine is certainly getting better than it was in high school.