Yep, a watermelon hill is a set of 2-3 plants that are allowed to sprawl. I plant mine in sets of 2's and redirect back to the "hill" as needed.
In CA we don't get vine borers, bit I seem to remember daily vine inspections mentioned on the garden forum but those who did, I think they had to locate the hole and use a pocket knife to cut out the larva before it killed off that arm of the vine, but again this is from memory. For the moths we do get here (hornworms, my son considers them his mortial enemy) I use a bug light zapper at night, hanging in the garden (specifically above the chicken run). No hornworms found yet this year, also no moths found, but I suspect that's because the hens wake first.