CB radio is very short range and line of sight. GMRS is longer range but also line of sight. In hilly surroundings you'll want to communicate through a repeater and since not many people are usually on GMRS, that leaves Ham frequencies. AdventureBound (above) gave you the best advice so listen to what he told you!
GMRS is far more common than CB today for general use. Many places have enough repeaters to make it a viable system if you do need to stay in contact with someone.
I have the Midland 15W with a 6dB gain antenna in my truck and it reaches as far as line of sight allows. They make a 50W but there is no where around here that would benefit from the extra power.
