Eight hours of sunlight is best, without it the plants will be tall and spindly and the blooms will be sparse and weak.
You can definitely pot some of them up, here is a great article about growing dahlias in containers
http://www.dahlia.org/index.php?page=growing-dahlias-in-pots

Thank you - good link!

My next question - the tubers are in plastic bags with wood shavings. SHould I leave the bags closed or open them. It is still too early to plant here - I'm thinking the first of May. Can the tubers hold in the plastic bags?

Those are wonderful dahlias. They stay very compact and don't get tall and spindly. I can't remember if I even pinched them but to keep them compact, pinch them anyway. You have plenty of sun for them. I feel for you with the Voles. I lost all my clematis. They just tunneled down and ate the whole thing. It had taken 3 years for them to cover the arbor and now nothing. I have tried everything with the voles but my dahlias are in raised beds. I have never had voles there. Good luck.