Print it and carry it
Two sheets, free, no account needed. Paper has one advantage over an app: it works when you are standing at a counter with someone waiting, and you would rather not be the person holding up the queue to unlock a phone.
The survival sheet
43 phrases for your first month — ordering, paying, asking where things are, getting help, and the replies you will hear back.
One page →
The signs and menus sheet
50 characters that do the real work: toilet doors, open or closed, the drinks board, what is in the dish, addresses and warnings.
One page →
Both sheets are Taiwan-specific throughout — traditional characters, Taiwan readings, Taiwan vocabulary. If you would rather learn them than carry them, the phrasebook has all 550 phrases free, and the reading module teaches the characters properly.