if you have time for only one ride, this is my recommendation. 90% scenic with max elevation just above 6,000 ft.
the drawback is that the starting point is approx a 45 minute drive north on the 8 fwy from the balboa park area.
there is a good size parking lot nw corner of the 8 fwy/hwy 79 intersection
only 3 stop signs-no stop lights on the ride. better direction (imho) is to ride counter-clockwise to get 80% of the climbing out
of the way early and to take advantage of lesser auto traffic.
if you want to lengthen the ride a little, you can incorporate kitchen creek rd (about 5 miles closed to auto traffic) but it's pretty desolate.
it would add approx 10 miles and 1,000 ft elevation gained.
or you can head north at the hwy 79/s1 (sunrise hwy) intersection and head to/from
julian for excellent pie and an additional 12 miles w/approx 500 ft gained.
the palomar/mesa grande area is great too but a farther drive from balboa park.
the great western divide ride in one of the strava links you posted is about as good as it gets south of the 8 fwy but the
better stuff is north of the 8. lyons valley rd is the most scenic in that area.
from the balboa park area, it's the better part of a 2 hr slog riding to any decent foothill/mtn scenery.
living next to balboa park, i've found that w/o driving to a spot closer to the foothills/mtns, you will
need to ride a century or close to it to get a decent mountain experience.
if you're not totally wedded to the idea of a mountain ride, you could do a lot worse than riding up the coast highway to carlsbad village or
the oceanside pier area and back. quintessential san diego county/southern california ride.