I live 500 miles north of DL (in CA, north of Sacramento). We have a creek and a pond on our property and mosquitoes are certainly part of the equation at times. We do have what is locally known as the Mosquito Abatement Program, which limits the time span in which it's a problem but doesn't completely eradicate it.
That said, I've never even thought about bug spray for DLR. I've never seen a mosquito there.