A proper cisco person? wow!
yeah, minicom would let you login to Cisco stuff no problems. but, linpus is a very cut down version of Linux and I don't know if it will come with minicom installed, it can be installed, but installing stuff on a linpus netbook is not straightforward!.
You also may have a problem with the USB-RS-232 device, there is a certain amount of support for those adaptors built into the linux kernel these days but not for all of them, and again, linpus is a cut down version of linux, support for that sort of thing is likely to be reduced.
I'd go for a windows XP netbook in your situation, they are still available and really cheap as they are selling of the last stock and it would work with your stuff.