CB frequencies (27MHz area) are good for extended range communication and are often better than VHF communication radios in hilly country, etc. Many police depts/ highway patrols monitor CB channels 9 and 19 unless there's way too much chatter (unfortunately often the case).
When I was a kid, I was in eastern Oregon with a 1-watt walkie talkie and I was talking to Las Vegas. [I was on a metallic roof - great ground plane!] But that's "skip" conditions.
CB's performance is a bit limited by FCC restriction on AM or SSB use only - it'd be real nice if they allowed FM for its quietness & better squelch action, resistance to fading, etc. SSB is sometimes better for weak signal work than AM but for emergency use you're often better off on plain AM to guarantee that you can talk to everyone.
You're limited to 4 watts output (which means about 7 watts DC input to final amplifier transistors).
DON'T BUY a 'peaked & tweaked' radio from a specialty shop. Most CB tweak guys don't know what they're doing and crank things up so much that a distorted signal results. An extra watt or two of power is not gonna help that much (doubling the output power only produces 3db increase - less than 1/2 of one "S" unit on your signal strength meter (if calibrated accurately).
Want more output? Get good quality coax cable and a big antenna. Ensure good grounding. Take power directly from battery - use two fuses, one on red, one on black power line. Those quarter-wave 104" ball-mount whips are pretty good, Firestiks are not to bad either.
AVOID the fancy power microphones, etc. - often useless: on many radios w/"MIC GAIN" controls the mic gain has to be backed off to halfway or less, which means that a power mic is gonna WAY overdo things.
I'd stick with a Uniden or Midland CB. They seem to have overall good reputations, QC, etc.
Radio Shack may be a valid choice too because their radios are pretty good and there's always a Radio Snack store around for warranty, etc.
[I have heard they've helped out travellers on warranty issues with radio swaps.] But if your antenna is set up OK you really shouldn't have any issues.
Bill Wiese
San Mateo, CA