I am PCS'ing to Vilseck, Germany in early Spring 2018. What is some important advice for a single junior infantry officer heading to USAREUR?

Enjoy yourself and travel. Vilseck is not a large city as I remember. There are plenty of opportunities to go see the larger cities. I once traveled to Regensburg from there and it was beautiful. Learn some German if you don't know some already. The Germans enjoy your efforts, and they are very helpful if you attempt to speak to them in German often replying in excellent English.

2LT (Join to see), it's great that you are reaching out to find out all you can. You should be assigned to an experienced Officer as soon as you get there who will help you over the barriers. Vilseck was my first duty station once I Commissioned. Took me forever to find it on a map! Enjoy your time there, travel often, especially to other European countries when you have the time. All of the surrounding countries are easily accessible on a three or four-day pass.

Apply for your travel passport now. Take advantage of the cheep travel (MWR and BOSS trips over 4 day weekends).
Be careful at the bars, 16 year olds are allowed. Don't be taken advantage of, Germans often think Soldiers make a lot of money and are looking for a husband.
Depending on your unit, you may be on mission quite frequently and in the field.
Enjoy your time, be ready for anything, and always willing to learn from those that have been in a while.