We are beginning to harvest our first luffas, but I am way down here in Louisiana, so I imagine ours were off to a much earlier start than yours!
With all of the foliage you have, it seems to me that you really should have seen some little luffas, but maybe not ...
One thing I know is that the female blooms (the ones that bear the gourd) won't be produced on the primary vine (the first to appear). The producing blooms will all be on the offshoots - the vines that grow out from that primary one. Sometimes you can get an earlier start on getting luffas by pinching the end of the primary vine after it gets about 6 ft or so ... this stimulates the other vines to get growing.
And as for how they look ... to me, they do resemble a cucumber -- very much so! The little gourdlet is behind the bloom, just like a baby cuke. You can see it easily!
Good luck, I hope you see some gourds soon! :)