Christmas/New Years is going to be expensive time to fly (it always is). Another option might be Southern California. Maybe a 8-10 day ride along the coast from San Luis Obispo to San Diego (yeah, its suburban but interesting). Its 'mostly' flat and 40 miles/day should be easy. Fly into LAX then take Amtrak up to SLO, when you return just take Amtrak from San Diego to L.A.(Union Station). I wouldn't suggest San Francisco to L.A. as SF gets a lot more rain than the Los Angeles area in late December/early JanuYou can still get rain in the L.A. area, but still less possibility than in SF.