Is it possible to take public transit and then hike to Whitney portal? Also wondering the same about getting to Horseshoe meadow without a car....
Not sure of the current status, but in the past there have been people offering Mt. Whitney Shuttle Service. You might check out East Side Shuttle @
http://www.eastsidesierrashuttle.com/ and see if they are still offering this service. Last I checked they were fairly high, with a surcharge for odd hour departure (2:00 AM for instance). However, far better alternative than trying to hike to either the portal, or to horseshoe meadows.
"Hitching" is common, and as far as I know is safe. Understanding your perspective might be different.
If it were me, I would go to the The Mount Whitney Portal Hostel and Hotel (located in Lone Pine) and ask if anyone was headed to the portal, and might they have room for you to go. Nearly anyone you encounter there will be going to or returning from the portal. Hikes are a friendly lot, and I doubt you would need to wait more that an hour to find a ride. Returning to Lone Pine from the portal will not be too difficult either. Either put your thumb out, or try going into the store and ask if any one has room in their car to take you back to Lone Pine.