I know that Fresno is the closest, however the prices are very high. Would Oakland, San Francisco, Sacramento or what be the best after that? We will be there in mid-March. Please advise if you have any help for me.

take whichever of those 3 gets you the best fare. the drive is a bit easier from Sacramento and Oakland and depending on where you are coming those two are often cheaper than SFO.

San Jose is also a possibility. Like Janis said, I would go with whichever one has the best fare.

If flying into the Bay area rather than Fresno, make sure your drive to and from Yosemite won't occur during the rush hours. You'll wish you paid the extra money for Fresno.

I just read that not everyone can drive into Yosemite. Is that true? We are renting a car and driving from the airport? Is that not a wise choice??

Mongolia,

That is NOT TRUE. From the offical Yosemite National Park web site:

"Yosemite National Park is accessible by automobile all year, 24 hours per day. Reservations are not required to enter."

http://www.nps.gov/yose/trip/travel.htm

Utahtea

There has been talk for a long time about limiting cars in Yosemite by having day trippers park outside and then shuttling them in and out. This hasn't happened yet though.

The only issue that you might hit in mid-March would be the possibility of snow, and chain requirements. The road through El Portal (hwy 140?) is the lowest and least likely to get snow, but there is still the possibility. Keep an eye on the weather reports, and it it looks like snow, you may want to pay the extra for a 4wd rental, as a surprising number of normal rental cars can't be fitted with chains.