March is perfect timing for coast and coast range. March is actually too early for Sierra. In my opinion, there are three nice areas to consider.
Henry Coe Park is the closest with good backpacking. It is rolling oak hillsides and although no big elevation gains, is surprisingly rigorous hiking. The trails go striaight up and down hills. If you choose this, you MUST get the most recent maps that show the trail systems. Topo maps are useless there. This area is surprisingly isolated once you get away from the first few miles with all its day hikers. Be aware that the north part of Henry Coe Park burned a few years back. They have a burn map so you can avoid the most devestated areas. Wildflowers should be out.
Point Reyes National Seashore is a bit farther, but if you want the ocean views, it is great, with good backpacking. It is definitely more crowded than Henry Coe, but not bad weekdays. If you do Point Reyes, be sure to go into the coast and drive up Hwy 1. Much more scenic than 101 even though it will take a bit longer. By the way, the hostel at Marin Headlands is a nice and cheap place to stay, as is Pigeon Point Lighthouse. There also is a hostel in Point Reyes. The road trip into the coast and up to Point Reyes is a nice trip in itself.
Third choice would be the Big Sur area. I do not do much down there so others may add information on this area.