According to IGN, PlayStation Vita 3G models in the US are able to pick up text messages due to a number being connected to your sim card. You can find them as Notices from Operator alongside the number of the sender. However, there's no way to respond to the sender and the number tied to your sim does no good neither. The mere fact you can receive them suggests something officially could come down the line - it's can't be there without reason.
Vita launches today in Europe and the US.