Just a word of advice from past experience. I would head as far south as fast as you can along the coast and then work your way back up through the interior. The interior is much higher elevation and, come March and April when the coast will be hot the interior will be a comfortable temperature. I am sure that you are having some very cool nights (maybe frost)right now in SMA and Guanajuato. This will apply to Morelia, Puebla, Oaxaca and San Cristobal as well as Guatemala, El Salvador and Costa Rica to Panama.