I've found 'Toko-Ri' near San Diego
After quite a search with Google Earth and the DVD, I've found where the real aircraft scenes were shot during the attack on "Toko-Ri". As the planes dive toward the bridges you can see the curves of Julian Rd, at a spot about three miles east of Ramona, which is about thirty miles north-east of San Diego. (33° 2'59.69"N 116°49'12.91"W)
Also visible in another shot is the valley which now features the Barona Resort & Casino. This is about seven miles south of Ramona. (32°56'16.60"N 116°52'18.29"W)
I would still like to know where the crash landing and ditch scene was filmed, but I am getting closer.