Hi,

I would say that 18F452 or 18F4620 is a great choice. If you want USB, sure it is the future but RS-232 is easier to get started with, you would have to use 18F4455 or something similar.

It more or less comes down to what you can get your hands on the easiest way.

If you plan to use serial communication it is recommended to have an external x-tal or oscillator.