Budapest in the spring is hard to beat. You get long days to walk along the Danube, outdoor cafés that are just waking up, and historic thermal baths like Széchenyi where you can soak in steaming outdoor pools while the air is still crisp. Heading over before the heavy summer crowds arrive makes it much easier to explore the city at a relaxed pace.
A typical trip runs about $2200 for flights, a central place to stay, and spending money. Since dropping that much at once stings, you might be looking at ways to split up the payments so you do not drain your checking account right before you leave.
That 0% window is a deadline, not free money. If you still have a balance left when the 18 months are up, interest kicks in on what is left.