I wiil be in the west coast during mid August. I can make a trip from LA, leaving early on Wednesday morning an returning Friday morning. Should I go to Yosemite or to Sequoia/kings Canyon ? Can somebody help with itinerary ?

Having visited both places (and absolutely loving both) I'd recommend Yosemite. It's just nothing short of one of the most OMG! spots on this planet.

My itinerary:
1) yesterday -- make lodging reservations in or near the park. August reservations within the Valley may already be gone.
2) Wednesday -- drive up to Yosemite, entering through Hiway 41 for maximum effect. Drive through Wawona as rapidly as possible, as you want to enter the Valley through the tunnel. When you do (and I am NOT joking) be certain that you pull off as soon as you first see the Valley. This is such an OMG! moment that you may not be able to safely drive the car. When you adjust yourself to viewing the Valley, start kicking yourself for allowing only one full day to see Yosemite.
3) Thursday -- keep kicking yourself for allowing only one full day to see Yosemite, but be certain to spend a couple hours at Glacier Point, preferably near the end of the day.
4) Friday -- as you continue to kick yourself for allowing only one full day to see Yosemite, start your planning for a visit that gives this place (and the Sierras in general) the time they deserve.

You really don't have enough time for either one, but you could see the highlights at Sequoia. I don't think you could begin to see all the highlights at Yosemite in a day. It would probably be better to do Sequoia in one day than Yosemite. You would certainly want to hike Congress Trail and see General Sherman Tree. Other things you might want to see would be Museum(30 minutes), Moro Rock, Cave. A good short hike upon entrance to the park is Potwisha Trail. I would lodge and dine at the Wuksachi. Lodging is ok, and the food there is very good. It is only about 10 minutes away from Congress Trail and General Sherman. Sequoia is basically a hikers park and then of course the trees. I would think the park would be less crowded midweek. Sequoia is much less crowded than Yosemite. We were @ Sequoia a month ago and played in the snow and walked the trees with snowshoes. Couldn't really do much hiking because of the snow, but really enjoyed the park. We ate at the Wuksachi 4 or 5 times and it was great.

I agree with paulrabe that Yosemite is one of the most amazing places in the world.You can certainly see Yosemite in a day, although you are not going to be hiking everywhere. I live about 3 hours from Yosemite and often go for a day and take our visitors. If possible, try and stay in the park...it really is an experience with bears wondering around at night...Take binoculars and when you see El Capitan, lay down in the field across from the cliffs and watch the hikers who are often in groups of 3-4 as they climb this massive rock.

Also agree that you should see glacier point.....just amazing! Have a wonderful time. I grew up in California and spent every summer camping in Yosemite....and for me, there is no better place to visit.

If I cannot stay in the park, should I stay in oakhurst ?

Yes, Oakhurst is a great location for the direction you will be coming from. Get reservations as soon as you can as all nearby accomodations fill early in the area.

Try the Tenaya Lodge, near the south entrance. www.tenayalodge.com

Weds: Drive to Tenaya, check in. Then go check out the Mariposa Grove of Sequoias, near the south entrance (you can take the tram up and hike down). After that, you can drive up to Wawona area.

Thurs: Up early, drive to the Valley floor, do one of the tram tours, maybe raft down the Merced, or take a bike or horseback ride around the valley. Hit Glacier Point on your way back down to the south entrance.

Fri: drive back to LA.

Of course, you won't be doing it justice, but you can get a little taste of the park, and see some of the "OMG" sites.