lurvley cucumbers and storing in sand

Acouple of questions that I'm sure someone could help me with?

-I've got 3 very healthy marketmore cucumbers which I am very excited about. Could anyone advise me of when the best time to pick them would be? They are about 10 inches long and very spiky! Is it still a bit too early? New to this cucumber lark.

- Also I am about to put my beets into sand for storage (as much as I love them I just can't eat them all quickly enough!) does the sand need to be bone dry?

Thanks all

I also would pick the cue now.  I have three plants and they have been looking really healthy and producing lots of flowers and then the cues started growing, so lots of excitment here as this is the first time I have grown cucumbers.  Then, for no apparent reason one of the plants just drooped and the leaves just hang down with no life at all.  Having two more I was not concerned as these were perfectly healthy with cues at about 8 inches long.  Then, another plant went the same way, droopy, lifeless leaves with the cues turning yellow.  So whilst the goings good, enjoy your cues.