obviously I might not be the best person to answer your questions, but I'm going to try :-)
We haven't had any safety related issues that I am aware of and we like to think of ourselves as being a safe place to stay. Since we are not in the center of Barcelona, we are a bit safer than others, but of course, we're not on "la rambla" so it has it's good part and bad part.
If you're interested in how others view our hostel, I can point you to http://www.hostelworld.com/hosteldetail ... lona-12156
There, the "Reviews" section is scores that our customers have given us, as you can see our "Security" rating is pretty good, so that might help. Remeber that that page represents how other hostelers view the Alberguinn.
Yes, the rooms have keys, but they are shared so you can't really lock them when traveling alone, since you will lock others out. If you were a group that had the whole room to themselves, there wouldn't be aproblem in locking the doors.
Hope to see you soon.