The map makes it look much farther from the main square, but it's actually not too bad of a walk. There's a shop at the bottom of the street and kitchen to prepare food if you would like to do dinner on the cheap. Many loud tourists pre-gaming but it quieted down exactly at 11pm. I guess there's a common rule for quite then. Which works because partiers can move on to clubs and others can sleep. The staff was very nice and gave us all the necessary information.
Your hostel is very lovely. The only problem I would say is getting there by bus. It would be very helpful if there was a sign for the hostel on the bus stop to let people know it is that correct one. As you say the locals were very nice but we had a huge problem finding Adria. Also you could mention in the directions that there is a road sign that says Bajnice on it and that would have been helpful to look out for. Also there is only one sign for hostel and its not very noticeable.
Great location! Very close to the train station and the directions they give to get there by walking from the station are very accurate, and make the hostel easy to find. Also its very easy to walk into the town square and see the lively part of the city. Yet come back to a quite place to sleep rather then trying to sleep in a loud city center hostel. Most of the guests were people staying for a night or two in Zagreb and then moving onto other parts of Croatia. Also the bus is a 10 min walk.