Southern California almost always snow-free:
- Catalina Island
- Channel Islands National Park
- Joshua Tree National Park
Snow pretty likely in March (maybe you like snow) PCT runs through it:
- Cleveland National Forest
- Santa Rosa and San Jacinto Mountains National Monument
- Mount San Jacinto State Park, via Palm Springs Tram or Idyllwild
- San Bernardino National Forest
- Angeles National Forest
Or come on up to the NorCal GGG XI in Henry Coe State Park near San Jose, and tack on a few days of backpacking.
— Rex