For career purposes, there is a lot of data you can find based on research provided by third-party firms that attempt to predict the languages that are most in demand. You can find this with a quick google search. However, that may only matter to you once you are closer to graduation.
My suggestion is to learn really any language as it will be a good starting point. Most languages are 80% the same, with some minor syntax differences, and really become interesting once you start learning the last 20%. I tend to tell people to study Java as from what I can tell it is the most dominate programming web language across multiple companies.
Lastly, if you are just starting out, I would see the policy of your local City College. When I was in high school, I was able to take City College courses for free. There were some rules like I had to be in a certain grade and then I could only take a certain amount of units, but it defiantly prepared me for college since I came in with computer science fundamentals. The other trick here, which happened to me by accident, is to actually look which of the classes in the local City College transfer to the college you want to go. This way you not only have a base, but you also come in with credits and are ahead of the game. To do so, check out http://www.assist.org/web-assist/welcome.html
The best language to learn is simply the one you actually follow through with learning. Once you learn one programming language, you'll have most of what you need to be able to pivot into other languages.
That being said, there are a few languages that make for good starting places. I'd recommend learning Python (an interpreted language) and C#(a compiled language) as they are both very established and popular. https://stackoverflow.com/questions/3265357/compiled-vs-interpreted-languages#3265602
Assuming the CS program you'll be participating in is somewhat modern, your classes will likely focus on either a variant of C (C, C#, or C++) and/or Java, any of which would be good to learn and will be useful after college.
An interpreted language like Python is also a good place to start because of how quickly it can be learned. If you're the type of person who needs to see results quickly to stay motivated, Python is a great language to start with and will be in use for a long time. You will need to keep in mind that it's far less "structured" than something like C# and that's a double-edged sword. It makes Python easier to get started with but some people miss out on fundamental concepts that a more structured language enforces and develop bad coding practices.