You can offer as low as you want, and see what they say. Perhaps those homes are vacant because they are overpriced. How long have they been vacant? One rental 2 doors down from me, which I previewed, $2350, is still vacant. I offered them $2100 in mid-December and asked them to update the kitchen. They declined, and still have no renter. Now they have dual payments, and I bet eventually they’ll reduce their price.
So I wonder if the rental houses are more valuable in Scripps Ranch or if the owners are just trying to get enough money to cover their mortgage. A low-ball offer will make them realize they are overpriced. Are you finding the houses on the MLS? A realtor can send you regular MLS rental listings, and then you can negotiate w/ the listing realtor and not offend the owner.
Have you considered Poway? My kids are also in GATE (you mentioned your daughter is in it), and most Poway schools have very involved PTA and Foundations. Poway schools have the highest test scores (after DelMar and LaJolla). The parents at the high-score schools raise lots of money for the schools, funding PE, art, music, and computer labs. There are lower-score schools, and I would avoid those (South Poway). Poway is a great family area, and sounds a little cheaper. Just a thought.