Here are the choices. Each with pros and cons requiring usage model (which you did not state) to choose properly:

1. Sprint international plan
2. Buy phone in Paris
3. Buy phone in the US (not mentioned)

For #1 to work, your phone model (which you did not state) must be one of the international phone (one with GSM SIM slot AND has 900/1800MHZ capability.) For current models, here is the list http://shop2.sprint.com/en/stores/intl_phones/international_phones.html. You get to this list by going down store/phones and check mark "international" in the left selection column. And you have to have the phone unlocked to accept non Sprint SIM cards.

Pro: You know how to use the phone.
Con: You must research if your phone hardware works.
Con: Depending on usage, it can get very expensive. For example, if you use data, even with data pack, http://support.sprint.com/support/article/Learn_more_about_International_Data_Pack_Addon/case-gz982789-20120511-112920 it can get expensive.

#2 always works in Paris.
Pro: low voice calls. Equipment is compatible for use in France.
Con: You have to learn how to use it on a fly, such as how to set the language to English if that is needed. You have to go through voicemail setup if you want it. Easy to use data capable phones are quite pricy.

#3 buy GSM capable phone with 900/1800MHZ capability.
Pro: low voice call cost. You know how to use the phone before you get there.
Con: Need to by a SIM in Paris.

Regarding #3, you don't need to buy a SIM in Paris. You can order a free starter SIM from Lebara from here in the USA, then top it up in France when it runs out.

Last year I got a refurbished Nokia international phone on EBay for under $30 including shipping. (Search for "unlocked quad cell" and see all the available phones.) Got a SIM chip with rediculously low per minute charges on arrival. Getting a chip beforehand would have been better as I would have known the phone number to tell home contacts, but a quick cheap text solved the problem easily.

Thanks all - one additional question, if we buy a phone in paris - would it include texting ?

It will include texting if you choose it to. But really, the cheapest way to go is to buy an unlocked quad-band GMS phone on e-bay or Amazon (I paid $26, and that was for a dual-sim phone so I can switch between my US and another - in this case French - sim), then order the free Lebara sim. I was in France in September for 3 weeks, used the phone constantly to call all kinds of French contacts (there's no charge at all if calling between Lebara customers), and the total cost was about US$12.00. I only did a few texts, maybe half a dozen.

^^
StCirq, Thanks for the tip. I am about to order the Lebara SIM for my unlocked blackberry - is this the link you used? http://www.lebara.fr/s-inscrire (It seems as if it's sold by all sorts of subcontractors.)

Oops - sorry - this is the one: http://www.lebara.fr/

I can't find the link that delivers to the U.S.

Yes, that's the right one. And there is no link that delivers to the US, but they DO! Just type in your American address, don't use abbreviations like St. (type out Street), and they will deliver it to you in the USA. It will come with your American address on it, and blow that it will say France

St. Cirq, Thanks so much for the prompt response. I just checked on Tripadvisor, and a few posters said it can take 3 weeks to arrive. I see that it is also sold on Amazon Prime (overnight delivery) for $29.95

http://www.amazon.com/France-Prepaid-Canda-Europe-minute/dp/B00ADSQ652/ref=sr_1_2?ie=UTF8&qid=1362347319&sr=8-2&keywords=lebara+france

Since I'm leaving in two weeks, that seems like a good option - what do you think?

Well, I got mine in 5-6 days, and someone else posted here a week or so ago that he/she got it in a week. I wouldn't pay $30 for it when the worst that can happen is it doesn't arrive and you pick one up when you arrive in Paris.

Yes, you're right. Thank you. I'm ordering two - one for Mr. Crosscheck who is going to the UK first and a French one for me. We're now debating whether to also pay for the Verizon plan on our iPhones, which we will have to use for receiving some calls/texts.

OP, sorry to hijack this!

<<which we will have to use for receiving some calls/texts.>>

Why? Maybe I'm not understanding, but why can't people call/text your French number?

I will give the French number to our kids and close work colleagues, but I work on many projects at once and it's awkward to tell every business contact that I'm out of the country.

Also, in an emergency, some people can't find/ can't figure out how to use foreign phone #s - after a tragic situation several years ago, we're just not comfortable if not easily reachable on our own US numbers.

We travel very often and like the iPhone/foreign phone combo - works well for backup and peace of mind.

Got it. Makes perfect sense. Thanks.

Your Verizon phone won't work in Europe, it uses CDMA technology not GSM.

Our Verizon phones are dual CDMA/GSM international phones and we have used them all over the world, including in many European countries.

http://support.verizonwireless.com/faqs/International%20Services%20and%20Roaming/faq_global_phone.html

our AT&T iPhones from the US work fine in Europe. turn off roaming and turn to airplane mode when not using. AT&T used to let you buy a discounted plan for calls and texts from Europe and you could cancel after your trip (7 or 10 days) but now you have to purchase the entire 30 days. So I just text using wifi, and keep the phone off...communicate via email and forget the phone except to call ahead for hotels, etc.

but crosscheck at very exhorbitant rates most likely. There is a simple solution, at least for receiving calls. Get a local sim card as above and open an account with localphone.com. They allow you tu buya phone number in just about any area code in the USA (assuming you're from the USA which you probably are as you have verizon) and then set up call forwarding from your verizon phone to the local number and set the local number to ring to your local sim...sounds complicated but it isn't and their rates are extremely extremely low.

Oh, that's really smart to set it up and set up call forwarding.

This all seemed so complicated to me at the beginning, but I'm starting to work my way through it, and there are lots of workarounds the costly US systems. I don't need to get calls forwarded, but it's still good to know. Thanks, xyz123!

Bookmarking. There are some great ideas here for the future. Thanks.