Does Android's Full Filesystem Encryption also Encrypt the SDcard? In Android's filesystem encryption do they also encrypt the SDcard? If so Is encrypting the SDcard optional or is it encrypted by default when you choose to encrypt your device?

Here's some info about Android's file system encryption and its crypto implemenation on android.com
Android provides the capability to do filesystem encryption, but it's up to the vendor who builds the firmware for your device to enable it for the SD card. I have only seen a few devices with this capability enabled for the SD card, though most seem to have it for the internal storage (/data). Typically if it's enabled, there will be a menu item in the settings referring to SD card encryption.

Here's the option for the Galaxy Tab 2 for example: