Waze, The excellent free GPS driving application is very useful in Israel, you can use it to get live traffic data and of course for turn by turn navigation. You should have a data plan with your Iphone or Android to use it and the app is free. Google maps is also useful on your smartphone but it is still not possible to use it for turn by turn navigation here. Google maps will show you live traffic data on highways.
It is possible to find a GPS Rental service in Israel. Some companies offer GPS Rental services with modern GPS units and Large screen 4.3 GPS for use in Israel just for less then 10$ a day.
The GPS systems are English speaking, just rent one and find your way easily with GPS. Some GPS rental companies offers 24 hours support line for users who may need help.
You may get a free delivery and pickup for your GPS rental from Ben Gurion Airport when you land in Israel.
I have been using GPS for a while and I find it very helpful in many cases even that I live in Tel Aviv for 10 years, sometimes it is the best way to get to that small restaurant or bar that you never seem to remember how to find exactly on your own.