Because yields decrease as day length increases, the earlier you plant the better. Just know that while it's not too late to plant now, your yields will not be as great as they will be for the gardeners who planted a few weeks ago. As a matter of fact, I plan to seed peas once every two weeks through mid-July. And I'm certain my yields will be more than adequate. Dakota' is a new 52 day variety that would make an excellent choice for gardeners above 8000' with a particularly short growing season.
Snap peas are the round pod type of edible pod peas.
Perhaps the most popular variety is 'sugar snap', known for very sweet peas and pods and long picking period. Sugar or snow peas have flat, crispy pods. They are a stir-fry classic and a welcome addition to any fresh salad, if they make it that far. I tend to eat most of mine right at the garden. Large pods develop strings, as do the snap peas.