My guess is that you'll probably have an easier time finding a USB sound card vs. a PCMCIA sound card, therefore it would probably be cheaper ... not to mention that you can take it with you and use ...
Hey, I've got a Dell Latitude CPIA-366XT laptop (366 PII, 128 RAM) and I'm thinking about a PCMCIA sound card that I could use to record guitar on and maybe play around with some bigger/better ...