best gps for driving in greece, but can also use in USA

Many people like Garmin; they have several models, some have Europe and North America programs installed. BTW, you really don't want to drive around Athens; a car is fine for the countryside, but use the Metro, taxi or walk in Athens itself.

Rome to Naples by train takes about an hour and a half. From the Naples station (Napoli Centrale), take the Circumvesuviana train to Pompeii (about 45 minutes if I remember correctly). Forget the car unless you plan to drive up into Tuscany.

I recommend the Garmin. I have used mine for 3 years and would use it in Greece. If you buy one, be sure you get the maps of Greece.

Buy it now so you can become adept at its use before you go abroad. There are web pages where you will find GPS discounted. Search for "discount GPS".

We purchased a Tom Tom 720 last Spring for use in Spain, Portugal and France. Tom Tom GPS comes equipped with the USA and European maps programed into the GPS (no additional purchase of maps required. When we arrived in Madrid and we turned it on and it sorted out the map of Madrid. Lessons learned: 1. It took a while for the GPS to cycle onto the Madrid map (it will not cycle in the airport--too much interference) and not all of the features worked until the next day--we arrived late at night and the concrete divider on the two lane ramps would force the particular lane to go the opposite direction from our intended route. Lost in the dark, after this happened several times the GPS took us on surface streets to our distination.The next morning the GPS showed the ramp splits and end of our miss-directions. 2. We did not have much time with the unit before we left and suffered through a learning curve trying to program form Seville to the Basque area. 3. You need to carry something like a paper clip to reset the GPS, which we would need to do if the battery was taken way down. It would not start even when recharged on some occasions unless you press the recessed reset button.
The screen is large enough to be seen when driving even with my old eyes--we found that a small bean bag will allow positioning the unit in what ever rental you have and we fashioned a shade to protect the view of the screen in the bright sun light. 4. We still used our Michelin maps--this helped when the GPS repeatedly tried to put us on a closed under construction toll road in Spain. Once we started on the alternate route through the mountains the GPS picked up the new route and directed to the destination on the coast. 5. The voice really helped when making directional turns in heavy traffic areas with lots of exits off of roundabouts that would occur one after another in Madrid. Use the unit when ever we out of our immediate area in Calif. Enjoy your experience!

We purchased a TomTom920 last year to use driving through part of France. We tried it out on a trip to San Antonio before going to Europe which helped us get used to working with it. We thought it was a great asset -- especially going thru all the roundabouts!! We also took a Michelin map along with us, just in case. Really just used the GPS. Just recently updated all my maps, so I'm ready to go again.

I recently purchased the Garmin Nuvi 780. Costco currently has them on sale for $250 (retail $499) after rebate. If you purchase it online from Costco you get the rebate immediately upon purchase. It is easy to use for a novice. Also has the voice directions.

I would also suggest you get the dash board mount if you live in California (windshield mounts are prohibited). Also a carrying case.

http://www.costco.com/
It is listed on the above link.

Here is a link to in debt review on the Garmin Nuvi 780.
http://www.gpsmagazine.com/2008/04/garmin_nuvi_780_gps_review.php