Croatia -> Montenegro -> Slovenia -> Budapest

Do you prefer this kind of pace generally?
I think at the very least cutting out the Kotor bay day trip would make sense--add that night to Zagreb.
Is Budapest just a departure point? Too bad, as it's a gorgeous city!

Be sure to plug in all the drive times on the viamichelin website so you will know how much time you have to work with.

Looks too fast to me - and I usually travel a lot faster than many people here think is reasonable.

One obvious problem: most of your days look like this:

wake up somewhere
drive to somewhere else
spend the night
repeat...

That's not smart nor is it sustainable for more than a few days. Worst, you spend all day in a car, you spend all your time getting somewhere, but you never have a day to actually spend anywhere.

You need to cut out some of your one-night-stands. A few one-night-stands here or there can be OK, but not a trip that consists entirely or largely of them.

It’s not an enjoyable pace for me. It’s not clear when you are hiring a car as you are picking one up on the 5 and 11 June.

With a car, Dubrovnik to Mostar will take c 3 hours. That gives you just over half a day in Mostar then the following day you would have a 3 hour drive to Sarajevo.

The 11 and 12 June are particularly rushed.

It will take 6-7 hours to get to Budapest and you aren’t spending any time there? It’s a 4 day minimum city, as there is much to see.

You appear to have perhaps 2 or 3 evening hours in Zagreb and half a day in Ljubljana. They're both very nice cities; I can't imagine rushing through them like that. By comparison, you have given yourself two full days in Dubrovnik, which is far smaller.

During the last nine nights of this trip you are changing hotels eight times. I would hate that.

I've used public transportation--primarily buses--through the Balkans on multiple trips, but it isn't terribly fast or efficient. International routes are pretty rare, and I'm always nervous about whether I've obtained accurate information about their schedules. It appears that you plan to use buses or trains to get from Sarajevo to Plitvice Lakes National Park. That will take all day, and it must be recognized that something might go wrong. With an itinerary paced like yours, you cannot recover from a transportation snafu.

Or perhaps you're planning to rent a car in Dubrovnik and use it for the Bosnia leg of your trip? That might work, but be sure the car-rental company authorizes travel through Bosnia. Renting in Sarajevo and dropping in Croatia would probably be painfully costly because of the international drop fee.

You've got to eliminate some places. I suggest cutting Slovenia entirely as it will be time consuming with very little time spent there. I"d even go so far to cut Plitvice and Zagreb, spending more time in the south of Croatia. Fly to Budapest then from Split or Dubrovnik. That trip from Sarajevo to Plitvice, for example, will be all day. Why would you do that?

Or cut out Mostar and Sarajevo and Kotor and Slovenia and focus entirely on Croatia.

Honestly, you have crammed three 12 day trips into one trip.

If you want to visit Bay of Kotor from Dubrovnik, there are some good affordable tours. I took one by Atlas Travel that I really enjoyed.

It appears that you plan to travel from Dubrovnik to Zagreb with 3 intermediate stops using public transportation or private transfers. As previously pointed out, public transportation would require a lot of time on trains and buses and allow limited time to visit your destinations. For example, going from Sarajevo to Plitvice using trains and buses could easily take all day. Even with expensive private transfers, I think your proposed itinerary would be very rushed. I also think you're rushing through Ljubljana, Lake Bled and Zagreb. So, "No" I don't think the June 6-12 portion of your trip is workable as proposed.

Thank you, everyone. Based on the feedback, I would see this is an option for the Balkan?

Dubrovnik - 3 days
Bay of Kotor - 1 day (day trip from Dubrovnik)
Split - 2 days (travel from Dubrovnik to Split)
Mostar/Sarajevo (2 to 3 days) - Mostar (few hours, en route to Sarajevo). Travel from Split to Mostar by bus.
Fly from Sarajevo to Ljubljana. Lj and Lake Bled for 2 days.
Lj to Budapest. I will continue in Budapest for a few days and travel to Poland ..

Skip Zagreb and Plitvice Lakes National Park. Do I miss much by skipping these two destinations? Any locations I shall add?

Thank you.

Plitvice and Zagreb are both good destinations. Plitvice is pretty magical if you see it at its best (which means spending a night there). However, like every other traveler, you have a fixed number of days. You have to skip a lot more wonderful places than you have time to include. This is why just about every traveler starts planning his next trip on the flight home (if not earlier).

You're moving considerably faster than I would, but you seem to have found transportation links that will work for this itinerary--no small thing when you're traveling rapidly through the Balkans. If you change one thing, there's a good chance you'll end up needing to change at least two others.

One thing I will point out, just in case you do decide to make a change: Zagreb and Ljubljana/Slovenia can very easily be combined. And Plitvice is a shortish bus ride from Zagreb. So if you wanted to drop Ljubljana this time around in order to have a bit of extra time elsewhere, you'd have a good chunk of a coherent follow-up trip read to go. (I'm picking on Ljubljana because I like it a lot and don't think you've allotted adequate time there.)

I suspect if I saw your whole itinerary, I'd be crying about inadequate time in Budapest and Poland as well as in Slovenia, but it's your trip and it has to fit your pace, not mine.

Just be very careful to verify bus schedules every step of the way, and keep in the back of your mind that there's a slight possibility the rug will be pulled out from under you and you'll need to scramble to keep the trip more or less on track. Do some research on back-up plans so you'll know your best option if something really inconvenient happens--like cancellation of the Sarajevo-Ljubljana flight.

Driving in Slovenia, Croatia, Bosnia, and Montenegro is easy and affordable. Just avoid a one-way rental with a drop in another country. With such a tight schedule, I'd drive most of the way. Pick up the car as you leave Dubrovnik and drop it in Zagreb and then get the train to Budapest.

I've driven Dubrovnik-Kotor-Mostar-Sarajevo-Plitvice before (not in one day!). Easy drive.

Plitvice is lovely and unique. If you go, do plan to get into the park at 7am when it opens, because it gets crowded with tour groups by mid-morning. Good strategy is to arrive in the afternoon, see half of the park late the first afternoon (crowds starting to thin) and the other half early the next morning. Park hotels (in the park, run by the park) are overpriced but super convenient, to allow you to walk right into the park.

Each to their own, if it works for you, go enjoy it.
A few comments though
Slovenia or Ljubljana to Budapest is a long train trip or a flight with a change.
BUT, from Podgroica its an easy non-stop discount flight
So, with that said

Jun 2 Sun - Arriving Dubrovnik (from Houston) at 5 PM. ON Dubrovnik
Jun 3 Mon - Dubrovnik free and easy. ON Dubrovnik
Jun 4 Tue - Dubrovnik free and easy. ON Dubrovnik
Jun 5 Wed - HIre a guide from Dubrovnik to Perast, ON Perast

Jun 6 Thu - Hire a guide from Perast to to Kotor (not great after Dubrovnik) Budva ON Budva
Jun 7 Fri - Free and easy in Budva
Jun 8 Sat - Guide to Stari Bar, Ulcinj, ON Ulcinj
June 9 Sun - Guide to the mountains, ON Tara
Jun 10 Mon - to Podgorica late in the day ON Podgorica
Jun 11 Tue - Podgorica to Budapest on Wizzair, non-stop under $100 in about an hour.
Jun 12 Wed - Budapest
Jun 13 Thu - Budapest
June 14 Fri - Budapest
June 15 Sat - Budapest
June 16 Sun - Fly home

in Montenegro, guides with cars cost about the same as a rental car in Western Europe.

But this isnt where you want to go. So, never mind.
But i have actually done this trip, more or less, took to visits to Montenegro to complete, cause i love the place.