Acceptable...any time. I think legally any time after noon. I know I've had my tent up in the hiker-in before noon.
Sunrise is the best time to be on this mountain. Make sure you look on the western horizon just after sunrise for the shadow cast by Mt. Whitney...I know this maybe a mid-September thingy but it is worth mentioning because it is a truly awesome sight.
^^^ Thanks for the response. It is good to know that we can get there early. Orignally We had planned on arriving at 5 am to get almost 23 hours at the portal before starting with the day hikers at 4 am the next morning. Looks like we are shooting for around 9am now unless I can convice the girls to go up to Horseshoe Meadow the night before.
Thanks for the tip on the Mt. Whitney shadow cast. When the wife and I made our first summit at sunrise our gaze was fixed to the east.
Welcome HT! Good luck with your plans! I hope you make that sunrise goal -- it will be memorable.
Now... be sure to read up in the Orientation Notes (link on the left) about the importance of acclimatization. Driving to Whitney Portal, spending the night, then hiking to Trail Camp usually brings on headache and worse symptoms for the majority of Whitney hikers. An extra 24 hours at Horseshoe Meadows or other high elevation place will help ensure a better experience.
^^^ Thanks for the response. The wife and I have some first hand experience with AMS. She got hit with it going up New Army Pass on our way to Mt. Langley. Then we didn't know why she was feeling sick.
I read on timberlinetrails.net that Campers, Motorhomes, Travel Trailers and other types of specialty overnight setups are not allowed in the Portal parking area. Do you know if this restiction is just for the portal parking area right in front of the trailhead or does it include the overflow parking area just below the trailhead parking? It would be nice to use our cabover at Horseshoe Meadow and then just park it in the overflow during our time on the mountain.