No Visa or TSA required for intro flights or demo flights.
Only if you are training for a license or rating.
Just let the fligh school/FBO clearly know that for now you are not interested in a ME rating for now. You are just orienting yourself.
Word of caution; flying a multi engine is very, very addicting....
The first time that you push TWO throttles up and accelerate down the runway is almost as memorable as your first solo.