It all depends on how fast you want to travel. January isn't a bad time to leave
California for
Mexico 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 during
hurricane season.
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.