To get a Taiwan motorcycle license (<250cc) you simply go down to the DMV and take the written test (all you need for 50cc scooters) and the road test (not hard). There are 3 DMV’s in the Kaohsiung area so it shouldn’t be difficult to find one in Taipei.
As far as learning enough to pass your license test just find an empty road or parking lot and get comfortable idling at low speeds. Motorcycles are a little more difficult but scooters are quite easy to drive. Until you experience the local traffic… If you want a nice place to practice take a weekend to Xiao Liuqiu (an island near Kaohsiung). You’ll probably need a license to rent but there’s very little traffic and it’s easy to scoot across the island. And it’s a nice place to visit.