Sabby is right (I didn't know you were old enough to drive. /ubbthreads/images/graemlins/smile.gif ) about the FCC. The regs for any 'consumer' service generally specify limits on power out of (or into) the RF amp, antenna gain/directivity, and communications distance.
The '2 mile' limit is sort of funny. It's not a guarantee or even typical (or possable), it's a *limit*. You're not allowed to use FRS to talk to people beyond 2 miles. Silly. CB is the same way. GMRS removes that restriction.
FRS limits are .5W out of the amp, 6 dbi gain from the antenna, and 2 miles communications distance.
GMRS limits (for handhelds) is 2W out of the amp, nor sure about the antenna gain, and no limit on communications distance. There are 'mobile' and 'base' specifications for GMRS as well.
One note on the GMRS licensing issue. Yes, you need a license to use it in the US and Canada (different licencing bodies, of course). Go, fill out the form, get a license. It's little pain and (as much as I hate saying this) it's the law. The FCC has very little sense of humor or sympathy for people who break these laws (as it should be). Especially when it's so darn easy to get the license. I'd be a bit cranky if you made me do a lot of paperwork to fine you because *you* were too lazy to do a tiny bit of paperwork to be legal.
I do disagree with Sabby with regards to getting good radios to start off with. Get a cheap pair of $20 radios ($20 for the *pair*) and try them out. You'll only need one set of batteries to get a feel for how you're going to use them. After that, if you need better, get it--you'll always have the cheap ones as a backup or for the kids to play with, etc. /ubbthreads/images/graemlins/smile.gif