If you're going to keep a journal (and I recommend it, if only to keep your memories alive and in order), I'd suggest either a notebook with a pen or a netbook.
I prefer to record my observations, etc., daily, at the end of the day. I'd already forgotten stuff when I tried to collect 2-3 days at once. Thus, for me at least, relying on public computers that might be spaced several days apart is a non-starter.
A notebook, one with paper pages and a pen or pencil, is always available. It's a decent choice, unless you plan to blog. The disadvantage is having to re-write everything to post it. OTOH, you're not limited in what you write, either by reasonable page limits, or by privacy and/or decency.
I prefer something with a decent keyboard, as Fred suggests. A long email on my smartphone is two sentences, and epic novel is three. On the other hand, I can fill up 2-3 pages from a good day on the road. If you're comfortable with a tablet device, that might work for you, but a netbook can be a good solution. (Beware, some netbook keyboards are dreadful, especially for people whose fingers are not skinny!) The netbook also saves half the weight of a bigger notebook computer. A netbook can save the weight of several chargers, although you may have to be in a motel overnight to get things charged.
One final though is that, if you're carrying a camera, you can back everything up onto the netbook. I did roughly monthly dumps to USB thumb drives and sent them home as backups, which worked well -- my camera and netbook both made it home just fine.