I was told that for any engineer Python is definitely the way to go. The syntax is intuitive and it is capable of doing a lot with data analytics. I am also in another class that uses R for machine learning (ISYE 601). It’s seem that both are good to know if you are interested in data science and machine learning.
It probably depends on your career path, but personally, I think being able to program in Python is the best skill to have, and everything else is more so a supplement to that. Python offers a plethora of flexibility in terms of its application, and having the knowledge of a major programming language like Python is very valuable. I think other languages like R are certainly relevant and can help to further demonstrate a strong technical acumen.
I would definitely agree with earlier posts that say R and Python, but I would also add that knowing Java is pretty handy as I found it to be a good base language that lets you learn other languages more easily. The first language I learned was Java, after that learning other languages was a piece of cake.