From Europe is cheapper to travel to Cancun and then to Tijuana. From Asia, maybe one stop in Los Angeles before Tijuana.
And from any place in the world, but Southamerica, maybe could be smart one stop at USA. And then flight to San Diego and cross the border walking into the Tijuana Airport.
Rosarito is a 40 minute drive from Tijuana Airport.
There are no trains and Mexico is a very big country. So plan carefully your journey. And if need some help just ask.