The Navtex from Split is your best guide at sea.
They don't use the term Bora. But frequently fcst strong NE gusts which don't always appear.The time to be careful is when the next ridge pushes the previous trough west. In fact I have heard a Croatian say "the Yugo brings bad weather and the Bora brings good weather!!" But strong Boras are not common in summer although not unknown as I can testify. In fact a slight Borino is a common morning wind and sailing in a light to moderate Bora (from the northeast) is common, and fine among the Croatian islands where the sea will be flattish. You do have to "mind the gaps" though, especially the longer ones such as from the tip of Istria to Losinj. However when the navtex forecasts 50kt gusts stay in Harbour!!
The pilot book (777ports or something similar) has a good section on weather and Lucian's website is very informative on all matters Adriatic.