My journey through Budapest is one of my favourite memories, and my only Eastern European destination. I arrived there on a night bus from Vienna, and one thing I had completely forgotten about was that the local Budapest currency turned out to be forints, not euros, and at that late hour, no money-changers were open. I had no cash to take any form of public transport. It was too far to walk, so I decided to take a risk and hopped on anyway, and hoped not to get caught by any conductors. I thought of a possible excuse in the event that happened, but luck was on my side.
Note #1: Always have a small amount of local currency to take with you to your next destination, to avoid landing yourself in similar situation above! At the very least have enough for a small meal and reasonable transport to your place of accommodation.