Do you turn your back to the pressbox to give these signals?

I do.

The important part of the signal is behind my back so that is what I let the pressbox see.

Yes, you should.

I don't have my book in front of me, but I assume one of the signals you mentioned is illegal forward pass. Here in PA, they have told R's that they want them to turn their back to the press box now for this signal. Personally, I think it looks better when the R doesn't turn (and they don't turn in major college and the NFL), but I'm not in charge.

According the the Referee Study Guide, for the illegal forward pass signal, we DON'T turn our back. For the sideline warning, we DO turn our back.

I agree only one I turn my back to is a sideline warning on the visiting team. Sideline interference and illegal pass I face the box and point towards the team it is against.