It all depends on how fast you want to travel. January isn't a bad time to leave California
and beyond but by leaving that late you will miss some of the prime time along the Mexican Riviera. Many cruisers will take their time sailing down to Zihautenejo and then prepare for crossing the Gulf of Tehuanapec in the spring. Most will try to avoid Central America
On the other hand, if you're doing a delivery
, January can be a good time to leave other than the storms from the Gulf of Alaska
which bring southerly winds. Those are easy to track and you usually have several days notice before one appears.
Fair winds and calm seas.