I'm looking forward to exploring Slovenia in a couple of weeks, including driving in the Julian Alps, Piran and karst areas. Can anyone give me feedback on whether using Google Maps on my mobile phone works fine, or should I pay the extra €10/day for a GPS from the rental car company? I have a good international plan with plenty of data at a reasonable rate, so would prefer just to use my phone, but don't want to get lost if there isn't good cell coverage in these areas.
I used my cell for google maps in Spain & Portugal March/April 2018; I did have my own GPS but it got us lost in Spain so I used my cell and got us where we wanted to go! This was the only time my GPS failed us throughout many trips to Europe. If you have a good international plan, go for it! I wouldn't pay €10 a day as it sure adds up.
I use this map app - https://www.ulmon.com
I have found it to be more accurate that Google Maps at the micro street level.
Read the FAQs - https://www.ulmon.com/frequently-asked-questions
I paid $20, but it appears that the price is only $12 now.
We used google maps last year with no issues at all in Slovenia and Croatia.
Another vote for Google Maps. It has worked fine for us in Slovenia and elsewhere. The data connection is very useful for avoiding or negotiating traffic issues. Remember you can download a map to use offline, thus using mobile data for traffic updates only (or not using data at all if you prefer).
I used Google Maps in Slovenia and Croatia in the fall of 2017. The accuracy was notably good everywhere we went, including Piran. I did not have a cellphone data plan, so I cannot comment on the cellphone coverage, especially in the mountains. I used maps that I had "downloaded for offline use" - which do not require a cellphone connection or a data plan.
- I ….. don't want to get lost if there isn't good cell coverage in these areas.*
Even though you will have a data plan, I would offer the suggestion to download the Google map of Slovenia for "offline use" so that even if you don't have cellphone coverage, the GPS will still work with the maps you've downloaded to your phone.
I'll also add that if I'm relying on my phone for driving directions, I download the same maps to a 2nd, backup phone (that of a travel partner or an old phone that you still have at home) in case the primary phone gets lost or broken. It will still function as a GPS if you have downloaded the maps for offline use.
Use Google Maps and get a cheap local data SIM (you can get 20/25 GB of data for just €10 from providers such as Hofer Telekom or Bob.si). There is good 4G coverage throughout the country, even in the Alps. That said, it doesn't hurt to download the area for offline use in the Google Maps app.