I should probably explain my previous recommendation a bit more. There are issues with using an HT:
1. The rubber ducky won't work well from inside the car.
2. The connectors on most HT's aren't designed to be continually connected and disconnected, and hence, if using an external antenna, there's a chance of breaking the HT's connector or simply wearing it out.
3. HT's don't have enough audio on receive for use in a noisy car. You may think your car is quiet until you try listening to an HT in one. This can be overcome with a simple earphone.
4. If you don't use a hand mike, it will greatly increase the strain on the antenna connector.
5. 5 watts isn't a huge limitation - you can buy a 35 watt amplilfier for about $100.
But, a lot of folks start out with an HT in the car. I just don't know too many that do it for long. I've had HT setups in the past, and they were "OK", but compared to a mobile rig, not great at all.
EchoLink, IRLP, Allstar and DSTAR linking - adding interest to repeaters worldwide 24X7