The weather started out very promising, about 55 degrees just before sunrise as I drove through Ocotillo. But it grew colder and windy as I approached the first trailhead, and only grew windier as the day progressed. Something like 30mph on the ridgetops which was enough to make rock-hopping a little dangerous. Too windy to really enjoy the summits and views, and oddly, the winds didn't help the visibility any - I would have expected crystal clear skies with such winds in the Sierra. It warmed up to about 68F in the valleys by the afternoon, but the wind made it seem a good deal cooler and I had a light jacket on much of the time. Obviously it could have been much worse - I could have been out there climbing in the 116F heat of the summer!
There are numerous sources one can use for finding the trailheads of these desert peaks. I had Jerry Schad's and Andy Zdon's books, plus some info from the HPS and Summitpost websites. The DPS guide also has information, all of which can be useful - these THs aren't always easy to get to. I had a 2WD van, no high clearance, so driving off the pavement was a challenge, and a took a significant amount of time as I came to find.
Jacumba Mtn
I followed Schad's directions to reach the TH as they were the shortest approach from I-8. Maybe not the fastest, though. There are several junctions not described in his book and I took one wrong turn that followed the RR tracks a bit too closely where they make a wide bend. There was much sand and some steep parts that challenged my vehicle enough to have me plenty nervous. I think the directions coming in from Mortero Canyon and through Dos Cabezas are the best option. The thing to know there is to not cross the tracks at Dos Cabezas as described in Summitpost (and I'll leave a note there shortly suggesting the same). Drive south for a mile and a half to an easy crossing where it's paved (albeit poorly) and you don't have to pile rocks up against the tracks to get over.
From
the trailhead, the main canyon heads northwest out of the parking area
rather than south or west as one may be tempted. There are several threads in
a braided use trail with a fair number of ducks that you can use to hike up the
main canyon to
Mortero Palms. This is a pretty cool oasis worth visiting on
its own. You can then follow use trails further west up
the canyon to 
a saddle
leading over to Goat Canyon. This seems to be the most popular route, and not
to climb the mountain, but to head over the ridge and down the other side to
view the Goat Canyon RR trestle. I didn't go visit it myself, but it is a
pretty impressive sight, I'm told (you can actually see it from Sombrero Peak
if you know where to look). From the saddle, I 
headed south along the
ridge to the summit of 
Jacumba Mtn. This took longer than I expected
because it is not a very direct route. More like following the shorter sides of
a right triangle.
On the return, I decided on a more direct route,
down a canyon NE of the
summit. This was a very enjoyable descent, with a few class 3 sections but no
serious cliffs or other hindrances. I found my way back to
Mortero Palms coming
from the south. I had hoped to get back to the trailhead more directly (perhaps
down that other canyon I was warned against in the beginning?), but this
worked out pretty nicely - it only took about an hour for the return. Car to car
time was three and half hours.
Sombrero Peak
I had trouble finding
the turnoff to Indian Gorge, driving 10 miles past it on
my way north on S-2 before acknowledging my mistake. If you're coming from the
south, you'll first pass Bow Willow CG, then Mountain Palm Springs, (both on
your left), then Indian Gorge/Valley about a mile further north on the road.
There is a sign at the
turnoff, not large, but large enough that I should have seen it. The worst part
of the road is before you actually get to the gorge, after that it is sandy but
much better. I didn't get to 
the TH until almost noon.
There is a ducked trail you can follow up the canyon, heading first southwest for a short ways, then steeply upcanyon to the south. There are several braids of the trail higher up taking you to the summit. It's not hard to find as it's only about a mile and half from the TH, almost continually climbing upwards. I returned the same way. Car to car time was just under two hours.
Mine Peak
This was the easiest peak of the day, and also the windiest. It was blowing like crazy. The peak isn't the highest in the Coyote Mountains, but it is the highest in the western part of the range (Carrizo Mtn to the east is a good deal higher).I followed the approach directions given in Zdon's book, driving 0.7miles to a junction, then following a left turn until just before the road drops down into a wash. I parked in a big open area to avoid some horrendous road for that last half mile to the mine. Even in 4x4 it would be a challenge as I noted rocks piled up in a few of the worst spots in an effort to get a vehicle over the obstacles. Better to park and walk the easy distance to the mine.
The abandoned 
West Dolomite Mine
is at the base of the mountain on the west
side. There isn't much to see there, not even an ore shaft. The rocks in the
area are interesting, lots of cyrstaline rock, some of it very sharp to the
hands. From the mine, you can follow a use trail up and around the right side
of the structures to the slopes above. Just climb uphill and you'll find the
summit easily enough - the highpoint is pretty obvious. From the summit one
has views to the north and east of the Badlands,
a badly eroding mix of cool rock
formations in the lowlands below. To 
the southeast
one can see the higher
Carrizo Mtn. To 
the west
are the Jacumba Mountains. I went back via the same
route, total time was about an hour and fifteen minutes.