Ya I was wondering hostels vs hotels or whatever. Hostel are the better choice and you should ahve a blast.
Oh and flights are a way better way to go. If you know the exact dates you are traveling you can get tickets that will be half the price of bus tickets. And they will take 2 hours instead of 12.
www.ryanair.com www.easyjet.com. The airport in amsterdam is super easy to get too also.
As for nightlife, I don't have any good advice. I've hosteled to all those places a couple times, and I generally just hang out with people I meet at the hostel, or go on a pub crawl or something.