I did a CTC tour in Slovenia a couple of years ago and can highly recommend it as a cycle touring destination. several highlights would be the Vrsic pass, the road up to Mangart (a mountain) from the Pradel Pass into Italy in the mountainous North and the wine area in the South. I seem to remember that there is a tick borne Encephalitis threat that may be relevant to campers and hikers but not to road bikers unelss you are wading about in the undergrowth, I seem to remember you need a vaccination but am not sure of this.
It is a beautiful (and affordable) place to visit, enjoy!