Piran

Too much? Can't say without knowing more. Where else will you be going? How long is your trip? What do you like/want to do/see? Where else have you been? Will you get other chances to visit this region anytime soon?

If you are planning just Ljubljana, Bled, and Piran...I would investigate other coastal options further south, in Croatia (actually, there's lots more to see in Slovenia, too - the Julian Alps, several caves, and more). Depends on how much time you have, of course.

Piran is nice enough - Slovenia has just a tiny sliver of seacoast - so if you're looking for a nice seaside town, and if you confine yourself to Slovenia, that's pretty much your only option (technically there are a couple other "towns" but they're all somewhat contiguous). But if you have enough time to go further, Istria (immediately to the south) is lovely and the rest of Croatia's coast further south is utterly spectacular.

If you can pull it off, personally I'd gladly trade 4 days in Piran for 4 days spent in Rovinj and Pula.

Piran is just lovely - a real gem. It would be a great place to chill and relax, if that's your goal - you can even go swimming there in warmer weather. But it doesn't take long to explore the town. Four nights would be too long for me unless I just wanted to relax there.

If you are looking for other places in Slovenia to spend time, there are plenty! I'm not sure how much time you plan to spend in Ljubljana (also lovely just much bigger than Piran), but I wouldn't shortchange your time there either. It's also a good base to explore nearby towns. Or you can stay in nearby towns too.

What is the rest of your itinerary?

I could happily relax in Piran for four nights. But I would have done all the sights in two nights and would need some reading to occupy the rest of the time. It would be great - at least outside the main tourist season. If that's not your thing, you could Piran as a base for some exploration.

We arrive on the 19th. We spend two nights in Ljubljana. We then go to Bled and spend 6 nights. Then Piran four nights . Nothing is written in stone except for arrival ion the 19th and leave on the 1st. We love nature and outdoor activities. But we love cities and museums. My big disappointment is the Villa Bled is booked. We do plan to drive through the Julian Alps while we are in Bled.

And we have traveled a lot through Europe but we have never been to Slovenia.

I would add a night to Ljubljana personally. I would not want to spend six night in Bled myself, either. People who enjoy the outdoors would probably prefer Lake Bohinj. Lake Bled is lovely but is a developed resort; Lake Bohinj is much more "back to nature" and less developed. Bled does have a town with restaurants etc. (many more options than near Bohinj), but I didn't care much for the town - it was OK and convenient, but at night I would much have preferred to be back in Ljubljana.

If I wanted to stay close to Bled in a town (not in Bohinj - I'm not much of a "nature" person), I might stay in the town of Radovljica, which Is lovely - much more character than the town of Bled. You can't walk to the lake from your hotel Radovljica, though, of course.

Try to drive from Ljubljana to Bled via the town of Skofja Loka (well worth a stop - you clearly have time to spend an hour or two there). The drive from Skofja Loka to Bled via the hill towns of Jamnik and Kropa is very scenic and beautiful - one of the highlights of all of my visits to Slovenia. Take your time and enjoy the drive if you can.

Look at staying in Ptuj. Agree with Andrew above that staying in the Bohinj area is a much better outdoors experience. We will be in Kobarid this week for four days and I’m excited about exploring the west side of Triglav and the Soça River. Don’t forget the caves either! Four days in Piran would be marvelous to me if you just want to relax. I’ve been to Piran a few times now, but we usually stay just to the south in Croatia.

Since you mention loving cities and museums: I'd consider shortening the Bled and Piran stays in order to spend some time in Zagreb. Lots of good museums and a very nice historic district.