"Who wants to go to this festival?"
Translation:Хто хоче їхати на цей фестиваль?
The word "go" in English is quite generic and I really like it! Basically, it means (in this context) that we need to get to the festival - and we don't need to specify how. In Ukrainian, you need to specify whether you "walk" there (йти-іти-ходити-піти) or "go in a car or using some other means of transportation" (їхати-поїхати).
Technically, you can translate this as "Хто хоче йти/піти на фестиваль?", but only if you're literally planning on walking there, which is highly unlikely in most of the contexts. So "їхати-поїхати" is definitely the best choice for this phrase.
Similarly, you'll translate "I want to go to Boston" as "Я хочу поїхати до Бостону", because it's very unlikely you're going to walk there.
I need to go to the hospital - as a person living in a large city, I'd say "Мені треба поїхати до лікарні", because I'll probably take a bus/tram/metro train to go there, but I can imagine saying "Мені треба піти до лікарні", if you live in a village, or the hospital is really close by.