My dad always had a guitar in the house - I screwed around with them for years, but never had any real formal training. As I got older, I taught myself a few songs here and there, and learned how to read guitar tab as a teenager (its a lot easier to read than music, but it doesn't tell you as much information).
If you have a local junior college that offers beginner guitar classes, try that. I did, and I had a lot of fun doing it. It's usually the least expensive way to learn, although you do have to deal with a group setting and homework, although a good guitar tutor will assign homework too. The guitar teacher at the school up here is a guy named Rob Bonner, and he's a total trip.
After two semesters of that, I decided to try playing in the junior college's Jazz band. It was VERY difficult, especially not being able to read music notation. I started taking private lessons to help learn the songs so I could keep up with the band. That helped a lot. I still have a hard time reading music, but now I know a little more about what I can get away with playing when I can't do what I'm supposed to ;P
You're never too old to learn a music instrument. Just don't go out and join a band before you're ready.
If you have Rock Band 3, the Rock Band 3 official Squire is pretty nice, and pretty cheap. And you can use it in RB3, or as a midi controller. And it is a REAL electric guitar. I just picked up the RB3 Mustang, which is not a real guitar per se, but a midi controller with 100-someodd buttons along a fretboard-like surface, and 6 strings that don't sound like anything when plucked by themselves. It's harder to deal with, because you can't feel in your left hand what strings your right is plucking, and all the fret buttons feel the same, instead of having a natural taper down in gauge like real strings.
If you don't own RB3, Squires are still a nice, cheap way to get started with the guitar. Places like guitar center often have deals where $100 or so gets you a Squire with a strap, a soft gig-bag, a cable, a tuner, and an amp - damn near everything you'd need. These are good enough for anyone to learn on. Protect your investment from the floor with a simple tubular stand or a wall mount.
My main guitar is a Sammick Sarc, a double-cutaway, semi-hollow-body electric. It has a nice, jazzy sound with a little chorus and reverb, and very fun to noodle around the scales, with or without an amp.
If you want to learn how to read music while learning guitar, look for
this book. My guitar tutor recommended it to me, and I found a used copy of it somewhere. Probably one of the best books out there for learning guitar from the ground up, while learning how to read music too (which isn't really required to learn guitar, but it sure helps when you want to play with a group.)