Jonah is one of my favorite prophets, and your question is interesting.  Hope this will be helpful to you and others. 

When we are trying to understand a particular passage, we can gain a lot of useful insight by using the basic rules of Hermeneutics - it's a 50 cent word for Biblical Interpretation. One of the most important principles is that we always look at the context.  
- that is, the historical context,
-literary context/ what genre of literature. 
- cultural context and 
- Grammatical context.  
We get some helpful information right away.  Jonah is not poetry, allegory, or wisdom literature, or apocalyptic literature like Daniel or Revelation. In the Old Testament, the 39 books are either Historical/Law, Poetry, and Prophets. It was an actual story by real people in a real city, and this is important because you can't take Genesis which is History and make it symbolic - which many people do. The text says that God spoke, God replied.  
Another basic rule of Hermeneutics is "If the passage seems to make literal sense, seek no other sense or it will be nonsense."  If we are reading historical narrative and it says there was a man on a donkey, then the reader should not imagine that the donkey or the man are symbolic.  So our first clue from the genre shows that there is no reason to speculate that Jonah had a dream, or vision.  To read something into the text that is not there is Eisegesis. 
Finally, another important foundational principle of hermeneutics is that scripture interprets scripture.  What other passages can we use to compare or shed light on this one?  
We have many examples of real prophets, who heard God speak in an audible voice and we see this over and over in the Old Testament. Samuel, Adam, and Nathan the prophet talked to God. Daniel,  Moses, and Abraham, Moses, and many other prophets or Old Testament saints talked to God. We even have descriptions of God's voice to Moses, and God speaking to the young servant Samuel. 
Also, we have many examples from scripture where people had dreams, or visions and heard from God in this way, and it is recorded in scripture. Jacob had a dream, of the ladder going up to heaven. Joseph the Husband of Mary, was warned by God in a dream, and if Jonah had had a dream, then it would have said this. 
I love that Jonah is the only prophet that Christ compares Himself to, and we have the sign of Jonah being in the great fish 3 days and 3 nights, and Christ actually quotes the prophet, and the only sign that he gives that He is truly the Messiah, is this sign - that the son of man is in the earth 3 days and 3 nights.  Hmmm.