I can empathize with you. We have rowdy neighbors too. Nice enough people, we're just different. Our kids don't exactly get along, either. The sunflowers are a lovely, civilized way of saying "good fences make good neighbors." Too few people in this world really understand the wisdom of that trite, but true statement. So much better than a cold standoff, or worse, outright hostility. After all, we have to live next to these people, right? I salute you and your sunflowers.
Ha -- we've already gone through cold standoffs & outright hostility. And it's not even my neighbor who's the problem! She's a solvent homeowner, after all. It's the disrespectful loser crowd that comes to mooch off her food & booze & boat that sets off the fireworks & steals my vegetables & races around on motorcycles.
Unfortunately, my neighbor ended up in the hospital recently, diagnosed with cirrhosis & emphysema, so she is totally on the wagon right now because she wants to live. And apparently she's not so much fun now for the partiers & things have quieted down quite a bit.
We were lucky that the former owners of our house had planted white cedar around the border of our land. Now the field behind us is being developed, so the cedar trees (now about 30' tall) form an excellent privacy hedge..