I text multiple people all the time. Just go to "Compose" a new text message and then add all the recipients you want to send the text message to. The phone will automatically default you to the message part after you pick your first recipient, but just select the "To" bar at the top again and you can add more recipients. It will save that "Thread" also so you can send multiple texts to that same group if you wish.
Also, i haven't tried it, but you can create Groups within your contacts and i'm sure that you can mass message a group if you wanted, if there was a specific group of people you were always looking to mass text.