1. Open up your text messages screen (the one where it shows the list of txt conversations by contact name.
2. click the menu button to bring up options
3. Select message settings
4. scroll down and you will find the vibrate for text messages option.
hope this help.
I'm not sure if this is just a launcher pro thing, or is the same with the moto UI, but I also found it really strange that through general settings/preferences you can change the ring notification, but not the messaging notifications. seems silly to hide all these notifications settings inside completely different access paths. DOH