Originally Posted by
Coffee
At least in Southern California and into the Sierra I think it is very possible and if planned well, public transportation could even be a possibility. I'm thinking in particular of:
Border to Big Bear: Park in Big Bear, public transit to LA, the onward to San Diego, bus to trail, hike north to van.
Big Bear to Acton KOA: Look into whether KOA will allow parking, or legit parking in town, public transit (train) to LA, then bus to Big Bear, hike north to van.
Acton to Walker Pass: Park at Walker Pass, bus to Lake Isabella, I believe there is connecting service to Bakersfield and LA, train to Acton, hike north to van.
Walker Pass to Lone Pine or Whitney Portal. ESTA from Lone Pine to Inyokern, bus to Walker Pass, hike north to van.
Lone Pine to Tuolumne: YARTS from Tuolumne to Mammoth, ESTA from Mammoth to Lone Pine, hitch to Whitney Portal, hike north to van.
There are probably other variations possible but I think this is totally doable, probably further north as well but I'm not familiar enough to comment north of Tuolumne. Good luck.