[xb95]

This is what I do/have done and it has worked well for me. I always bring my laptop and if they ask me to write code (as they invariably do) I pull it out and use it.

That said, whiteboards are still usually better for conveying ideas. If you don't understand the problem you're trying to solve or the data structures you need, you might want to start on the board before sitting down to code.