I am studying in Spain next fall and would like to travel a bit before my classes start. I would like to visit France, Italy, Germany and Poland. What are my options for reasonably priced travel? Would it be cheaper to ride by train or fly? Do I have any other options?

I’d like to be able to dress in light clothing but a sweater is okay.

Please give me a accurate statistics of European number os tourist visit per year together with the link. Thank you.
It is BEST for those link to have an English version. I can’t read French.