Mexico is easy to reach with direct flights from Germany, eg. Visa upon arrival may be obtained simply and are cheap. Traveling by taxi, bus or aircraft is quite cheap either and driving your own vehicle is no problem at all since the road are good and police controls are friendly although frequent.
A word about safety and security. It should be clear that you better avoid overlanding in certain areas, Guatemala border, eg. For well known reasons Mexico is known as one of the most dangerous countries in this world and I was honoured by SES accepting the job. After 42 days in many places in Mexico we may state that we never ever encountered any problem with safety nor security. We were never attacked, robbed or even agressed. Moreover we felt rather ignored most of the time… We are experienced travelers and do not know much about Mexican society and social behavior, maybe we are naive and if you are a scary person…