There are 2 routes into Borrego springs coming down Montezuma's grade OR taking the long way around to scissors crossing, staying on our more southern route, THEN cut back north after you get down the hill.
All that said, IF you go down Montezuma's grade (aka S22) it's a more direct route BUT the hill is long and you'll want to use the engine to slow you as much as possible. Pretty steep but certainly doable with a few turnouts to get folks around you. IF you like scenery and looking out over the valley all the way to the Salton Sea - this is your route. If on the other hand, you don't like guard rails and steep cliffs (some don't) then see the next route.
The other direction - going up the hill out of Escondido is not bad and needed (SR76), then cross on both routes to the 79) , but you'll stay on s2 and pass s22. That takes you to the 78 (I don't recommend taking 78 through Julian), then head north on S3 or for a more leisurely and not much more mileage, go to Borrego Springs road and head north.
Heading down to the state campground down in Borrego Springs by chance?
2017 Winnebago Vista 29ve