Those green beans will make vines.....LOTS of vines! I am glad that you made a string trellis, it's the easiest way to grow and then do the clean up at season end. I use hay twine, then cut it all loose, fold and stomp until I can sack it up in a garbage bag. Or I could spend countless hours of enjoyment picking vines off wire.....NOT!
The first year I planted them, they made tons of vines. The vines raced to the top of the trellis, grew into a wild tangle, massed up and fell over. No blooms. No beans. Aaaallllllll summer! Nothing. I got mad and gave up. September......well, maybe I still watered the monster vines......BLOOMS! I got excited! The Vine Monster finally had blooms and made green beans.
I planted them in the same place the next year, true to form, they made tons of vines, but bloomed and made green beans much sooner. Those freakaziod vines made beans until a HARD killing frost in
DECEMBER!! 
I got sick and tired of durned green beans! These are the zucchini of green beans!
Don't despair if they don't do much the first year. Just keep them watered and see what happens.