I second the suggestion of Octillo even on pavement. I went from San Diego out there on my 1200 Bandit and it was awesome in a middle of nowhere open kind of way. Its been a few years, but I cant imagine it has changed much. I cant give you much in the way of highway suggestions since its been awhile, but anything out there should be nice.
Watch out for jack rabbits! I was headed back towards the mountains to get back to the freeway (8) towards San Diego and the shrubbery on the highway started moving in towards the road. I thought to myself "man, not much reaction time here" and literally about 8 seconds later a jack rabbit ran out in front of me and I nearly hit him. Full panic stop and swerve- no good! This was just after dusk, so..
If your looking for twisties, anything in the Julian area is fantastic. Lots of highways to explore. Taking 79 down from Temecula would be a nice highway ride..