If you want to use public transport you have to buy a special card called Urbana. You can only buy it in specialy designated areas which are shown on the map in the file below ( bus lines map). The important thing to know is you have 2 types of Urbana card. You can buy the tourist one which costs 23eur and includes admissons for 15 Ljubljana tourist sights but only 2 bus rides. The second option is you buy an "empty" Urbana card for 2eur which you can than charge for whatever amount you choose. One bus ride costs 1,20eur and is considered to last 1,5 hours. You can change as many buses as you like in that time span.