The way out of Leon is very well marked, but you are right: the continuation is VERY bad: Highways, thundering traffic, etc. Almost all the way to Astorga. Disgusting. But 7 kms after Leon there is an alternative: Take left at the end of La Virgen del Camino and walk to Villar de Mazarife. Stay there. Next day is a peaceful walk all until Hospital de Orbigo, almost in Astorga. Highly recommended. No need for a taxi: Just walk out of town and take the alternative route.
I forgot to write: By taking this Way, you are walking a great Way all until Hospital del Orbigo. At the end of Hospital del Orbigo, you come to a crossing, giving you the possibility of going straight on, or taking right to Villares del Orbigo. Take right, and enjoy yet another peaceful walk all the way to Astorga. I recommend it. Villares del Orbigo has 2 albergues, a bar, and is a very nice little village/place to spend the night, giving you a nice 17 kms walk the next day into Astorga.
Our fellow Forum member,
@LTfit , purchased an albergue there: A very nice place. I stayed there when the former owner was running it, pre-Covid. Unfortunately for
@LTfit , she opened it on March 11, 2020. And on March 12, 2020, heavy Covid restrictions arrived in Europe. Everything was shut down immediately.
We were several pilgrims who tried as best we could to assist to our ability, but to no avail. The pandemic was stronger, and lasted longer...
But anyway, this walk is easy and peaceful.
By taking these two diversions, the walk from Leon to Astorga is tranquil, except, maybe, for those first 1.5h., 7 kms. No big deal. Skip the bus, not the Camino, IMHO.