It's best to get an International License. It's fairly easy and cheap I think, and you don't need to have a driving test, just some minor paperwork; just "google" it. Your Intl. Driver's License should be for an automobile which will cover any scooter (50 ccs). Helmets are required.
Seriously, cabs are cheap, the buses are nice and the subway is awesome. I live in LA now which is a third-world country by comparison.
In the countryside, rules and laws are more lax so you may get away with not wearing a helemt but it's best to respect the laws of other countires. Please be mindful of that and don't commit "Ugly American or Canadian" acts. That made life difficult for me in the 6 years I lived there. Assholes who didn't respect the locals and made us Westerners look bad. Anyhoo, remember that it's a crowded country so personal space will be limited. You'll notice people bumping into you constantly while walking around and if you do get a scooter, you'll notice that the law of the road is the bigger vehicle has the right of way and that everyone will cram to fill every nook and cranny. So as a pedestrian, be careful too.
I would check out Lonely Planet's Taiwan and Culture Shock: Taiwan for a loose reference.
I kept an open mind, respected the locals and enjoyed the 6 years I lived there. Just remember, "When in Rome..." and "Do unto others..."
I'm sure you'll have a blast!
*Edit: add - here are the links for Intl. driver's Permits etc. watch out for scams.
http://www.caa.ca/indexm.asp - Looks legit, I linked it from your government's site.
Here's another useful link too-
http://www.voyage.gc.ca/main/pubs/taiwan-en.asp I don't know what you're doing there but the basic info is ok.