I ended up taking roughly the route posted here, but not quite exactly it. The only truly big change was taking I-5 through the Grapevine (max elev. ~4000ft) instead of the side roads (somewhat closed in winter) through Frazier Park (max elev. 7000+ft). Here were the maps I carried (and mostly followed), plus commentary:
Day 1,
http://ridewithgps.com/routes/4028428: As planned, except I hopped on a semi-parallel bike path from southern San Jose down to Gilroy. Path was fine, but not as consistently flat as roads would have been. CA-25 into Hollister is well-trafficked and well-traveled, but there's a solid shoulder for cycling, so no safety concerns. Beware: the Pinnacles Campground store isn't necessarily open at the hours claimed online. (No issue for me, I planned for this.)
Day 2,
http://ridewithgps.com/routes/4028320: As planned. Jayne Ave. out of Coalinga has a moderately small shoulder, and the road's rather cracked (every some number of feet, can't remember exactly), but it's ridable even if bumpy -- just glad to get off it. Paso Robles Hwy. into Lost Hills has a lot of traffic but also a
very wide shoulder, so no biking worries at all.
Day 3,
http://ridewithgps.com/routes/4028328: As planned. A very little bit of the road between CA-166 and I-5 was basically sand, but we're talking a couple dozen feet or so at most. I-5 was incredibly nice to bike, given what one might expect of biking on an interstate -- the shoulder is pretty much the width of a lane, and once you hit the ascent all truck traffic takes the two right lanes. The speed differential between traffic and me went as low as 5-10mph at times (and I was going 5-10mph myself). Plus for that route there were three chances to move out of traffic (the weigh station pulled through before the ascent, two water stops along the ascent). Still, it was good to get on a surface road after nine miles of it.
Day 4,
http://ridewithgps.com/routes/4028348: As planned. I detoured into Lancaster to pick up a spare tire (I fixed a flat just after the CA-14 overpass, then noticed after installation that I should have replaced the tire as well, so I picked up a second tire to be ready for that
) a couple miles, no other changes. CA-138 is a highly-trafficked road, but the shoulder's good, so it's not dangerous. CA-18, on the other hand.... The first four or five miles are fine, shoulder's reasonable. Then after that the shoulder goes to maybe a foot, traffic gets bad, and you
really don't want to be on it. (Especially at dusk and into darkness, as I happened upon it. Oops. But given my knowledge, at that point my only option was to stay on the bike, keep pedaling, and get through it as fast as I could.)
http://neilhanson.com/2011/day-5-frazier-park-to-victorville/ claims there are side roads north of CA-18 that are preferable. I
highly recommend finding and taking them.
Day 5,
http://ridewithgps.com/routes/4028362: I opted for a motel on 7th St. instead of staying at the park, so that changed route a little. From there I started Hesperia (truck route, not pleasant for riding, particularly in morning but manageable) to Bear Valley then back on route. CA-18 this day was far, far better than yesterday. I made a last-minute decision and abandoned route at mile 56 to travel around Yucca Valley: left on Linn, right on Belfield, left on Reche, right on S. Border Ave., right on Golden St., left on Sunburst to end up in Joshua Tree. (All these roads were paved, tho most back here weren't.) If you don't like highway riding, you want to take these mostly-empty roads instead. From there CA-62 into Twentynine Palms has traffic but a reasonable shoulder.
Day 6,
http://ridewithgps.com/routes/4028367: As planned. The start of the day was an easier 92mi than I'd expected it to be. (Possibly because my only point of reference was 84mi in high summer in Nevada/Utah, probably 15-20 degrees hotter, but even adjusting for that...) From Vidal Junction into Parker has lots of truck traffic: unideal, but manageable. The shoulder's not great for riding, so I did a lot of riding on the road until a truck appeared in my rear-view mirror, then moving onto the shoulder til it passed.
Day 7,
http://ridewithgps.com/routes/4028377: CA-95 is well-trafficked at the start, but at least it's short. I don't remember the status of the shoulder, except that I wasn't too put out by this stretch. Only thing of note: find a place to stay in Wickenburg in "advance" (not sure how far, probably call around beforehand). The first four or five places I found were all full. I stayed in one of two open rooms in the Super 8 (the queen suite, at least triple my needs for space, but oh well), and the other room filled up before I left to find dinner.
Day 8,
http://ridewithgps.com/routes/4028420: More of the Arizona Canal Trail than I'd expected is unpaved hard-packed dirt, and nearby surface roads aren't ideal for cycling. I coped. Most of the road cycling in the Phoenix area was amidst much traffic. N. Scottsdale Road has a variable amount of bike lane on it. If you're moving reasonable fast as I was, it's not too bad, but not exactly pleasant. Adobe Road near the end had some brief sandy bits, but not enough to get off and walk or find another road.
As far as overall route reasonableness goes, it got the job done, and it had some scenery to it. It's not the sort of roads that will make you love long-distance touring: shoulders vary, traffic levels vary, distances between towns were rather large. But it worked. The only big change I'd make if doing it again would be to get off CA-18 into Victorville as soon as possible. CA-18 was worse than I-5 for biking -- crazy but true.
Also of note: there were very long daytime headlight sections on this route. I haven't investigated the case law, but at least by the letter of the law that applies to bikes. Plan headlight capacity accordingly. (I had a 350lm headlight with somewhere under 6h capacity in two batteries, tho I think I only ever needed one. I switched on flashing-brights mode in these sections.)
