Driving into Piran

I don't have first-hand experience with dropping off luggage at the hotels, but I have been to Piran numerous times and from my understanding, you'll most likely have to pick up a parking ticket. There is no payment machine, but there is a manned booth at the exit from the old town area. Either the hotel will give you some sort of confirmation slip or you will simply tell the operator you are guests of the hotel and had dropped off your luggage. At worst you'll have to pay €3 for staying in the centre for up to one hour. After exiting the restricted area, enter the parking garage, leave your car and then it's a very short walk to the free shuttle stop that will take you back into town. I believe the open-air parking lot is for permit holders only, or at least it was the last time I was there.

As for parking your car at the hotel - according to Google Street View, a section of the parking lot opposite the hotel looks to be reserved for guests, yes. It says so on the no parking sign. It's the four yellow spaces marked H where the red Porsche is parked on Street View.

Edit: Clarified my experience with parking

Thank you very much, Dejan. I'm much less confused now.

As we've now returned from our trip to Slovenia, I thought I'd describe how the "driving in Piran" experience turned out. In short, almost exactly as Dejan described it.

We collected a ticket from the barrier on entering the town and drove, slowly, round the harbour to the Hotel Piran. The hotel's reserved spaces across the road from the entrance were all occupied but we could park on the street in front of the entrance to check in.

Once checked in, we followed the hotel shuttle to the parking garage. At the exit barrier, which is staffed, we handed in the original ticket and a card from the hotel, so the brief drive through town was free.

When we departed, we paid the hotel for parking (at a discounted rate) and took the hotel shuttle to the garage. The shuttle driver saw us out of the garage and we were on our way. Absolutely no problem.

I'll add a couple of general comments about the driving. We rented from Sixt at Ljubljana airport and returned the car to Sixt at Ljubljana rail station. The return location was poorly signposted and rather difficult to locate but the rental itself was hassle-free.

Lastly, on arrival we drove from the airport to Kranjska Gora. Google Maps fortunately warned us of several kilometres of tailback at the entrance to the Karavanke tunnel, so we drive through Jesenice to avoid it. It looks like congestion is frequent at that point, though I couldn't tell if it was simply a delay at the top plaza or temporary Austrian border checks.

Despite not entirely co-operative weather, we thoroughly enjoyed the trip and will recommend Slovenia to everyone. We are now dieting.

I am happy to hear that you enjoyed your stay and the parking worked out fine.

Lastly, on arrival we drove from the airport to Kranjska Gora. Google
Maps fortunately warned us of several kilometres of tailback at the
entrance to the Karavanke tunnel, so we drive through Jesenice to
avoid it. It looks like congestion is frequent at that point, though I
couldn't tell if it was simply a delay at the top plaza or temporary
Austrian border checks.

It's a combination of both occasional border checks, increased traffic and construction in the tunnel. The queues are not daily, but will likely occur on a regular basis until the second tube of the tunnel becomes operational in 2023. Fortunately, you used Google Maps and avoided the delays. Similarly, if you follow traffic announcements on the radio or online (also in English), they will instruct drivers to Kranjska Gora to exit at the preceding junction once the tailbacks reach a certain point.

Thanks again, Dejan. I must say Google Maps' more or less realtime info has proved its value over the car's own satnav more than once, not just on this recent trip. It also highlights the benefits of the new EU rules allowing us to use our data allowance across borders.