We understand your concerns but from our perspective things doesn't look so disorganized. Yes there is still a lot of missing points but at least there are well defined general guidelines about travel. Zagreb --> Banja Luka are very well connected with buses so even if you come to Zagreb without any preparation, you would not have any difficulty comming to Banja Luka. (Although i believe you will have all necessary guidelines on time.) Just please don't make panic.
Also, today Adnan presented DebConf11 organization at ODRS/CLUC event in Zagreb (
www.dorscluc.org) and invited more more people to join travel team and help with those issues in case you are coming via Zagreb. People ware very interested in DebConf11 today so i have no doubt there will be some volunteers from Zagreb helping about this issue.
best regards.