Best Strategy for Voice/Text/Data - 10 days between France and Germany

[inquisitor]

Originally Posted by Guthdog

The LIDL card is at $.09/minute and my friend in Otterbach can pick one up for us in Germany and pass it to us when he meets us in Paris.

If possible ask your friend to buy the Lidl SIM card as early as possible and to send you all the numbers printed on the plastic card through which you could already activate the SIM card from the US. If you follow the activation instructions here you'll receive a referal credit of € 5, which however may take up to 3 weeks to be accredited. That's why you should activate it as early as possible so you get the bonus before you arrive in Germany.

@Inquisitor - Mobiho looks very attractive from a cost perspective, but I don't read a word of French! Is there a data plan that can be added to the voice services?

It seems like Mobiho don't offer any data service. At least I couldn't find any related information on their website.
If you need data Ortel mobile may also be interesting. They offer calls to the US for € 0.11/min, however all calls are subject to a connection fee of € 0.15, while data is billed with € 0.25/MB: Ortel mobile - France (the French call megabytes also "mégaoctets" from which the abbreviation "Mo" is derived)

Per your earlier post, with any of the major carrier networks, I shouldn't really have to be concerned with coverage in any but the most remote locations, correct?

Yes. In France there are four wireless carriers (Orange/France Telecom, SFR, Bouygues and Free), which all provide outstanding coverage (except Free who have only launched their network this year but have a national roaming agreement with Orange and don't offer any prepaid tariffs anyway). For coverage maps see:
Orange Intense - Couverture réseau 3G
La couverture du réseau SFR en France métropolitaine
Couverture Bouygues Telecom
All prepaid products you find in France are based on one of these networks. For a list of all MVNOs including the underlying radio access network see Liste d'opérateurs de réseau mobile virtuel - Wikipédia

In Germany the situation is pretty much the same where four networks (T-Mobile, Vodafone, E-Plus and O2) provide nationwide coverage with very few white spots which you will hardly find as long as you stay on paved roads. T-Mobile and Vodafone run more basestations and so have slightly better coverage, especially when it comes to 3G, but Otterbach and the wider Frankfurt metripolitan area are definitely covered by O2's 3G network, which Lidl makes use of.