I'm tackling the section between Poway and Vista in this thread.
I'll start with Poway and the road into Escondido.
As I mentioned in the last thread, US 395 followed Old Pomerado Road north of the Poway Grade. The center of this area (north of the creek) was called Poway Grove Park during 395 days.
The main road into the village of Poway in the first half of the 20th century was not Poway Road but Oak Knoll Road. From there you had to go north on Carriage Road (appropriate name) to Poway Road. The main town area was between Midland Rd and Garden Rd where all the car dealerships are today. The area near the junction of Carriage and Poway roads was the location of the main Kumeyaay-Ipai indian villages. There is a Pauwai indian village interpretive site on the hill to the west of Carriage Rd off Poway Rd. Open Saturday mornings.
US 395 proceeded straight north from the intersection of Oak Knoll and Pomerado. The jog east at Twin Peaks Rd/Camino Del Norte has always been there. In the early 1900s it was a series on angles, and in the 395 days it was curved, but the curves were sharper (smaller radius). The road seems to have run a bit farther north into the flat area, then curved more sharply east.
The 395 highway followed all the curves of Pomerado Road to Lake Hodges. One thing to explain, however, is the path of the Inland Route to Escondido before the Bernardo River was dammed in 1918 forming Lake Hodges (and Santa Ysabel Creek as the feeder's name today). When the highway reached the area around Bernardo Trails Drive, it veered northeast into the canyon on the east side of the hills east of Pomerado Road. A dirt road still exists in this canyon leading north to the Pinery Christmas Tree lot. From there the old Escondido Road bent west, meeting a road coming in from the west side of Battle Mountain. (Farther south it's essentially West Bernardo Road). After the merge, the road headed north in the area of Evergreen Nursery off Highland Valley Rd. It was roughly where the nursery's main road is. It headed north to cross the Bernardo River on a bridge. On the north side, part of this road still remains as the Mule Hill hiking trail. Mule Hill north of the lake was the site of the final stages of the Battle of San Pasqual. Just north of the bridge, near where the hill comes closest to the dirt road, was a small town called Bernardo. Traces of this old Escondido Road are visible as ghost signs painted on the nearby boulders advertising businesses in Escondido. This dirt road then headed north becoming Sunset Drive (now part of Bear Valley Parkway in this area). The road stayed with Sunset Drive as it turned northwest. Bearing left at two forks, the road eventually merges with Escondido Blvd, once called Nutmeg.
Here's the 1901 map around Lake Hodges, with notes:

And here is the same area in 1947 right before the freeway alignments were built. This is the way the highway looked from 1926 to 1947.

After crossing the old bridge, the road followed the same path as I-15 until Centre City Parkway. It followed Centre City until Escondido Blvd (Nutmeg) veers off to the right.