Firstly, the Geo and Explore are the names of older Eye-fi cards that are no longer in production. Because they are no longer in production the rest of my answer will disregard them.
Now if I understand your question correctly you are asking if you can connect to an ad-hoc network where an ad-hoc network is a network that is in existence without any dedicated infrastructure nodes(read routers).
tl;dr Yes they can connect to an ad-hoc network.
If you were to create an ad-hoc network on say your laptop you could connect your Eye-fi card to the network created by your laptop and configure the card to automatically upload files to a folder on your computer for viewing.
However, this may be more hassle than it is worth considering Eye-fi has produced a feature called "Direct Mode". This seems to be similar to what Itai mentioned with the Toshiba FlashAir. Basically you can configure you Eye-fi card to broadcast a pre-defined wireless network that your computer can use to receive photos from the card. Then your card would upload directly to your computer. Please see the full details at http://support.eye.fi/features/direct/enable-direct-mode-to-computer/
I feel it is also worth mentioning that Eye-fi has also produced apps for iOS and Android that can enable the same direct mode photo storage and viewing on your mobile device.
It is also important to note that if the Eye-fi is able to access another trusted network it will choose to upload pictures to your computer, the cloud, mobile devices, etc. instead of using the direct mode network. You still get the same feature just without the ad-hoc network. I suspect this is to reduce the battery drain on the camera due to the card broadcasting a network vs connecting to one.
I hope this helps. I have had a good experience with my Eye-fi card (Connect X2) and I am currently thinking about buying a Pro X2. Having the automatic backup to flickr/my computer is a nice piece of mind. The endless memory feature is also pretty awesome.