Unlocked Quad-band GSM Smartphone under 150

When I search Amazon for an unlocked phone with GPS, the choices are limited. I think that is a product of the search function, though. The problem with some, apparently, is that they lack the radio bands for the newer, faster connections (3G, 4G, LTE) and that is upsetting to some folks. How do you plan to use the GPS? Over a cell connection or only when you have a wifi connection? If it is over cell, you may want a phone with more than the old GSM European bands (900 and 1800 mHz), which otherwise will limit you to slower data speeds. (Handling data on a cell is a whole other topic that I won't touch on here.) I'd stick to a phone with one of the major operating systems to ensure you can access things such as Google Maps. In your price range that likely means Android. You may have to settle for an older version of Android (e.g., 2.3 instead of 4.2.2, which I think is the latest). You may find a better deal buying it over there. I'd check out tigerdirect.com, too, and Best Buy, too. Tiger Direct has some clearance phones that might fit your description of what you need. For comparison with what may be possible overseas, check out carphonewarehouse.com. As far as I know, it is a British company, but there are likely similar stores in France. Good luck. Let us know which phones you are looking at in particular and we can give you more specific advice.

Thinking about it some more and looking at the limitations imposed by your price point, I have another question: Do you want the GPS feature as the primary reason for the phone or are you looking for a smartphone to do all the things that a smartphone will do? Have you thought about a small tablet, such as a Kindle Fire or Nexus 7? You could get one of those for something around your price and then either get a very inexpensive phone to use in Europe as a phone, or, perhaps better, a cellular based wifi hotspot. That you can purchase for less than the cost of a phone and then you could use it to connect your tablet anywhere you had a cell signal (of course, you'd have to get a prepaid SIM from some European company or a travel phone company).

I have iPad with AT&T cellular plan. I want a phone mostly for GPS and make calls for reservation.

Why not a stand-alone GPS unit (e.g., TomTom or Garmin) and a low-cost prepaid phone purchased over there? That would fit in your price point and keep you from having to settle for a really out-of-date smartphone.

Another source of unlocked GSM phones is AT&T's "reconditioned" units. AT&T will also rent you a phone, and you can catch a county's SIM card in Europe. I just communicate through WiFi on a laptop/notebook @ hotels when traveling out of the country. We're going to Halifax Tuesday, and Canadian cellphones operate the same as Europe as far as calling back to the U.S. If I'm making hotel reservations on the run, I'll go into a hotel lobby or pull up under their canopy to pickup their WiFi signal.
I actually like not talking to anyone on a cellphone for a couple of weeks while on vacation.