Official language is Slovene.

The vast majority of Slovenians speak Slovene. Its a Slavic language very similar to Croatian and Serbian and somewhat related to other Slavic languages like Polish and Russian. Second language for older people was Serbo-Croatian language, but for most population its English.

In some muncipialities where minorities live, Hungarian and Italian are also official languages. A small minority of Slovenians speak Italian mostly in the area near the Italian border. Smaller minorities speak Hungarian and Croatian. English is very widely spoken as a second language along with German, Croatian/Serbian and Italian.

The only official language is Slovenian , or Slovene .
Most of them speak Slovene..In some schools students speak even Hungarian and Italian.

So people speak many languages here, because in Slovenia, there are;

83.1% Slovenes ,

2.0% Serbs,

1.8% Croats,

1.1% Bosniaks, 12.0% others and unspecified
The Slovenian people speak Slovenian/Slovene, which is very similar to Croatian, Serbian and other Slavic languages.
They speak Slovenian, and Serbo-Croatian
People in Slovenia mainly (more than 95%) speak in Slovenian language. Slovenia also has two minorities: Italian and Hungarian. Those two languages are also recognized as official languages on the territories where those two minorities live. There is also a quite large community of people form ex-Yugoslav republics, who came to Slovenia looking for work. They may speak Serbian/Croatian.
Slovenian people speak Slovene, a South Slavic language.
Slovenian. (Slovenščina)

However, by law they are bilingual on the coast (Slovenian and Italian) and in the area near the Austrian border (Slovenian and German).

During Titos administration, the unifying language of the area was Serbo-Croatian, so all public schools in what is now (and was prior to the Former Yugoslavia) Slovenia, taught Serbo-Croatian and Slovenian.