Can they be eaten raw?
In salads etc.
Oh yes! You can grate them or make them into ribbons with a mandolin or potato peeler. I would avoid using the middle spongy bit though.
twinkletoes
If spongy, they're too big?
yes get them little; say three inches and slice very thin, they are lovely.
My kids eat them instead of cucumber in a salad.
You can slice them, grate them. Mix them with nuts or freshly chopped mint, or mayo all sorts of variations.
ENJOY