Need help with planning 18 day trip.

Have your booked your airline reservations yet? Why R/T Zagreb? That means you have to backtrack and that wastes time. It would be better to purchase open-jaw or multi-city tickets. For example, fly into Dubrovnik and home from Zagreb or vice versa.

Yes, it is a lot of locations. It sounds hectic to me but I am much older than you and prefer a slower pace. For example, this was our itinerary in 2019:
Dubrovnik - 3 nights - included a daytrip to Bay of Kotor
Split - 4 nights - included a day trip to Hvar Town and 3/4 of a day to Trogir
Plitvice - 1 night
Zagreb - 2nights
Ljubljana - 3 nights, included a daytrip to Lake Bled

We didn't go to Istria but I know a lot of people say it is a long drive to get there so you should spend some quality time there, not 1 or 2 nights.

I think you can visit Krka from Split for a day. And it looks like you could visit Zadar as a day trip from Split.
https://www.chasingthedonkey.com/how-to-get-from-split-to-zadar-croatia/

You should plan your trip in nights. So do you have 18 nights?

Since you have been to Lake Bled, perhaps omit Lake Bled so you will have more time in Rovinj and Pula.

If you start in Dubrovnik, a possible route would be Dubrovnik, Korcula, Split (with daytrips to Hvar, Zadar and Krka), Plitvice, Istrian Peninsula, and end in Zagreb to fly home from there.

Having a car will help rather than relying on public transportation. Driving in Croatia is very easy.

I hope this helps.

Rovinj is a wonderful little coastal city and there are several hill towns nearby for a nice day trip. We particularly enjoyed Grožnjan and Motovun. Also, Ljubljana is definitely worth a visit if you're going up to Bled.

12 destinations in 18 days? Sounds like an opportunity to create memories of being in a car and finding parking. Slow down. Create an itinerary creating the opportunity to experience the destinations rather than seeing the locations. Forthrightly most of the coastal destinations are better accessed via ferry. Slice your destinations in half and create some wonderful memories!

Hi Jeffrey,
The route I would take is: first Zagreb to Lake Bled. ( Lake Bohinj is only 30 minutes further and is really beautiful too). Then Rovinj via Ljubljana. (You may want to check out the unique architecture n downtown Ljubljana). Rovinj to Pula. Then Zadar, Krka National Park. Sibenik is only 20 minutes from Krka and is an awesome town. Then to Split. Plitvice Lakes National Park is about 2.5 hours from Split. To miss the throngs of daytrippers in Plitvice from mid morning to late afternoon, try staying overnight. You will have Plitvice to yourselves the next morning when it opens.

You could return the car in Split and just take the catamarans linking Split to Hvar ( 1 hr away by cat) Hvar to Korcula
(90 minutes) Korcula to Dubrovnik (2 hrs) From Dubrovnik, you could fly home with an open jaw ticket, or return to Zagreb for your return flight home.
A heads up; the seawater temperature during May before the sea has warmed up averages between 60 and 65 degrees. July through September is optimal for a trip centered on swimming at Croatia’s beautiful beaches.
Have. a great Trip!

Just curious, where is Zitha or is it a typo?

Thanks for the help.

I think I got it planned now.

5/4 LAX to Zagreb

5/5 pick up car rental in Zagreb and drive to Bled.

5/5-5/9 Bled

5/9-5/10 Piran

5/10-5/12 Rovinj

5/12-5/13 Plitvice Natl Park

5/13-5/15 Split

Ditch car in split

5/15-5/18 Hvar

5/18-5/21 Korcula

5/21-5/23 Dubrovnik

Fly Dubrovnik to Zagreb

5/23-5/24 Last night in Zagreb then LAX

I was wondering if it would be worth it to remove Korcula and Plitvice and add more days in other places.

I have not been to Korcula so I can't comment on that. But we have been to Plitvice Lakes National Park, which is stunning and very unique. If it were my trip, I would not omit Plitvice.

Thanks I might keep it how it is then because most drives are only an hour or 2, besides Plitvice.

I would keep Plitvice Lakes National Park in the plan.
I would give three nights to Lake Bled and add one night to Piran. Be sure your hotel has parking available because there is none inside the old town itself. On the way to Piran, I would stop at Skocjan Caves which has a 90-minute tour of these amazing caves. Rovinj for two nights ( Are you daytripping to nearby Pula from Rovinj?)

Then Plitvice Lakes. One of the lodgings at Plitvice offers a deal of admission for the afternoon of the day you arrive, and also the next morning. This is exactly when you want to be there as the throngs of day trippers are there from 11 am to 3pm.
I would add one night in Split. Before you return the car you might make a trip to Trogir- another Venetian town worth a look that is 30 minutes from Split. Three nights in Hvar is fine. Hike up to the castle above the town. Take one day and take the bus to Stari Grad to see one of the oldest continuously-inhabited towns in the world. The Romans were here in 200 AD and you can see Roman mosaics being excavated from underneath the cobblestone sidewalks in Stari Grad..
You asked about Korcula. It is an amazing stone town with its ancient walls, gates and towers all Intact. It’s quite different from Hvar, but it is quite small. It is impossibly romantic and a great place to spend a couple nights with your wife before continuing on to Dubrovnik. I would add a night to Dubrovnik to make it 3 nights. Take one day to go to Lokrum Island- a National Park where you can hike to a fort with panoramic views that Napolean had built. There’s also a historic monastery which houses the “Iron Throne” from the Game of Thrones series. Pack a picnic lunch and make a day of Lokrum Island.
Have a great trip— Croatia 🇭🇷 is awesome!

Wow thanks for that advice kenko. Sounds like that’ll be the plan then. Definitely want to see stari grad and was thinking of doing Pula if we had enough time.

Jeffrey, There are actually three hotels at Plitvice Lakes National Park that offer the “One-Day Ticket” to the Park. The ticket is available only to hotel guests and allows you entry to the park on your arrival day AND the next morning. So, you can enjoy Plitvice once all the tour groups have left the park in the late afternoon, and the next morning before they arrive about 10:30am. This is why overnighting at Plitvice is key to enjoying your visit.
The three hotels are: the Hotel Jezero, the Hotel Plitvice, and the Hotel Bellevue. The Bellevue offers the least expensive rates (about $100 for two in May).
These hotels are nothing fancy, but they offer free parking and quick access to the National park which is what the visit to Plitvice is all about.
Have a great Trip!