Tyreese and his group are awfully trusting of new people, considering what they said they'd been through on the road. Interesting direction they're going in by having them side with Woodbury, though.
I hope the father and son get done in pretty quick, they're just plain dicks. First trying to get Tyreese to help them take over the prison, and then actively offering to help the Governor take down Rick's group. Hopefully the Gov will use them as cannon fodder.