How do I prevent iPhoto from starting every time I connect to a camera card?

In the iphoto Preferences disable "connecting Camera opens" - set it to "No application".

If that does not suffice, do the same in Image Capture:

In Image Capture - with your camera card inserted- click the disclosure triangle in the lower left corner of the window to reveal the menu to set the preferences for the device:

Then set the option to "Connectiong this ... opens" to "No application"

You're welcome! 🙂

Be prepared to have to do this for each of your cards, since Image Capture will see each card as a different device.