If a building is near by, get in it, your pgrens can still shoot the panzershrecks and will be protected from the T-70 because of the building.
You can also try and trick your opponent by trying to time your panzershrecks upgrade meaning... charge the T-70 with your panzergrenadiers when the shreck upgrade is almost finish, he will maybe stay close to your pgrens hoping to kill them because he doesn't see any danger but you'll then pull out the panzershreks and kill it

If you are going for a Teller mine, keep it between the T-70 and an easy pray to serve as bait, like an MG-42 and obviously there is more chance if planted on a choke point.
You also have the ability to cloak your panzergrenadiers from the commanders Jaeger Infantry or Storm.
BUT, I would try to stall it as much as possible and go for a PIV, if your opponent spent fuel for a T-70, he shouldn't have anything armor wise to counter your PIV afterwards.
If your early game map/fuel control is poor, expect armor and save for panzershreks or paks.