Cold resistant plants?

Cold resistant plants?

I was sorting my seed packs out and noticed that peas, lettuce and other things say "plant in early spring." Does that mean they'll be ok if we get a couple of frosts or do I need to wait and plant them with things that say "after last frost?" I've never grown most of this stuff before so I'm a little lost. I'm eager to get things into the ground straight away but I will cry if everything dies if we get a cold snap. We live in Zone 7.
Finally!

Finally!

Useful Tree Recommendation

Useful Tree Recommendation

The grass really IS greener on the other side!

The grass really IS greener on the other side!

Summmer squash blossem

Summmer squash blossem

Bluebells

Bluebells

My livingroom

My livingroom