I taught my friend to ride EUCs in about 2 hours. He already knew how to ride a Onewheel and is an active MTB racer.

We started with the white Swagtron Swagroller. It has dual wheels so it's more stable side to side. After he got a feel for mounting and turning, he worked on riding the Inmotion V8F which is one of the biggest selling wheels internationally. He was interested in buying a bigger wheel, the RS19, so I let him try my Inmotion V11. The pedals are high because it has suspension. He wasn't quite comfortable riding the V11 but you can see that he was able to do it.

If you're in the market for an EUC, I recommend buying from a reputable vendor like eWheels, who will be able to supply parts and cover warranty claims. You can use my affiliate code if you shop at eWheels.
http://www.eWheels.com/Ben