Another alternative is to take an airline bus from MUC to the train station (hauptbahnof?). I think it cost 8-10 dollars or marks, can't remember. Of course its Euros now. This was recommended to me by a local because its a little bit quicker and easier if you have luggage. I think they call it the Lufthansa bus but anyone can take it. A cab from the airport would be expensive--at least $60. The trainstation is centrally located and a cab to the park would be minimal.
I did travel on teh U-bahn in Munich and found it easy to use, clean, etc.