Hi Mark. Not sure if helpful, but below I am pasting in the Istra Peninsula portion of our (my wife and I) visit to Croatia in 2017.
We really enjoyed it. Full report is on the forum at the URL at bottom.
Aug 29 - Sep 1 (3 nights): Rovinj. Perfect length for us. Most of the tourists seemed to be families that had driven down from Germany. We flew out of the Pula Airport when we left. Very small - the rental car dropoff is right next to the terminal building.
We stayed at Baron Gautsch, from the Rick Steves guidebook. Very nice. Our room was air-conditioned, located next to the upper-floor large balcony - which we usually had all to ourselves. The balcony overlooks the old city of Rovinj, and the sunrise views are glorious. Breakfast was excellent; if one is leaving before breakfast, the staff prepares a bagged breakfast for you. Never had a problem finding parking.
During our stay we walked the old town of Rovinj (beautiful at sunset), drove to the Hill Towns, and visited Pula.
- Hill Towns. MOTOVUN, ZAVRSJE, and GROZNJAN. TIP: visit MOTOVUN early, before the crowds. We arrived shortly before 11am, and were able to park close enough to walk into the town (rather than take a shuttle). The views are stunning. We had an incredible lunch and local wines on the terrace of Pod Napun (mentioned in the guidebook). TIP: arrive before the crowds to get a good seat along the terrace. We then drove to ZAVRSJE, largely deserted. The road we took passed by the site of the former train station; the track route is now a hiking/biking trail. We spent about 30 minutes walking through the abandoned village. Next; GROZNJAN. Good last stop. Mildly interesting. We did a quick walk through the town, browsing at a couple of the artist shops.
- PULA. One day we drove to Pula to see the Roman artifacts. The amphitheater, along with the small museum underneath the arena, was worthwhile. We then walked to the Temple of Augustus (as described in Rick's book, do view the back of the adjacent bldg), the Roman Floor Mosaic - difficult to find, and the Arch of Serguis. We drove along coast to return to Rovinj, stopping at Farzana for lunch.
On Sep 1, we flew out of Croatia from Pula.
https://community.ricksteves.com/travel-forum/trip-reports/croatia-road-trip-aug-2017-dubrovnik-and-drive-to-split