Vienna and Salzburg are best in late winter. You skip the spring crowds, the streets are quieter, and you can actually get a seat at a coffee house. The air is crisp, and the atmosphere feels local rather than tourist-heavy.
We can look at breaking that $2500 cost into manageable pieces. If you use the Discover it® Cash Back, you get 0% intro APR for 15 months on purchases. This gives you a clear window to pay off the trip before any interest hits.
Remember that the 0% intro APR is just a window, not free money. If you have a balance left over after 15 months, the bank will start charging you interest on the remaining amount.