I hope you like big crowds, long lines, bad service, hiked prices...
best trip is to 7/11 to get beer and than go back home.... avoid traveling in china.
As others have said, don't do it!
Guilin will be rammed...the new high speed train from GZ to Guiyang has already sold out for all of Spring festival.
Sanya? Have you seen the photos of the shit left behind on the beaches in previous years? You won't be able to move for local tourists and their litter.
Harbin - don't know how busy it will be but it'll freeze your nuts off!
I went to Vietnam last spring festival, 1500rmb for a return flight from GZ to Ho Chi Minh (with China Southern), good value hotels and a moped to whiz round on was 50 kuai a day. Plus good weather and nice food. Took long distance buses to visit Mu Nei (ok beach tourist area) and also Nha Trang. Wouldn't go back there again but it was good getting out of the city.