Hello,
I am planning a trip to visit Barcelona, Madrid, Budapest, Vienna, and Prague.

Day 1-3 Barcelona
Day 4 AM Barcelona -> Madrid (train/flight?)
Day 4-5 Madrid
Day 6 Madrid => Budapest (flight ~3 hrs)
Day 6-7 Budapest
Day 8 Budapest => Vienna (train ~1.5 hrs)
Day 8-9 Vienna
Day 10 AM Vienna => Prague (train/flight?)
Day 11-12 Prague


I believe Barcelona to Madrid and Vienna to Prague by train take approximately 6 hours. Few questions:

1) Would it be better to take train or flight for these 2 segments?
Barcelona-> Madrid / Vienna -> Prague

2) I used cheaptickets.com to look up flights, are there any other websites/resources that have budget plane tickets?

3) As we are still trying to finalizing the cities we wanted to visit and # of days, I hate to book tickets and end up have to stuck with the dates. How early should I book to avoid being charge premium?

4) For point-to-point rail travel, can I book these if I live in US?

Thank you!!