I know many people have been wanting to text groups. I use this function at work on a regular basis and was really disappointed that I couldn't do it......I've discovered how to do it!
1. Download Handcent Messaging app it's free
2. Go to google account and edit contact list as desired. Create groups, etc..
3. Sign into google account on your droid, it should auto synch, (I don't think you will even know it happens)
4. Open Handcent , press upper left 'compose message icon'
In the To: box on the right side there is a green + sign , press that, on top you will see three tabs, Contact/Group/Recent press group, select the appropriate group you created in your google account on your pc.