1. You'll get internet access if there is somoene who has an unencrypted router which means you'll have to fish for someone careless. Essentially you can steal internet if you try.
The easiest way is to get DSL or Cable with a WIFi router and you can run that all you want. Or go to coffee shops etc.
2. A 32Bit PCMCIA Wifi Card is better than a USB card becuase it's a little lower in profile and you won't snap it off accidentally. It varies though as some of the USB units have more features since it can afford to be thicker than a triscuit.
3. Any card is good. Your concern is security. Make sure you have a good firewall up since people can hack the wireless card and have access to your machine when your card is operating.
4. Better to get a name brand one which are 54Mbps such as D-Link, Linksys, Netgear, etc so that the software will get updated years from now. Others just buy and pray it works beyond the store return policy date!