Yes. DO it. It's important. Code for fun, code for interest, code code code. Just remember that the main objective right now is to learn things and sharpen your skills, so don't get too hung up on external validation/objectives for your coding projects.
You can learn a lot of stuff at university, but the prescribed path isn't going to do it for you. You need to seek out the interesting people, interesting projects, and interesting opportunities to really learn stuff.
University of Washington is a good school, and tough. I'm not saying this is going to happen to you, but community college can be a very different place from a top 4 year university.
Also, will your transfer credits count towards your major, or as prerequisites? In many cases, they do not. You may find that despite having enough credits to be a junior, in order to satisfy the requirements of your major you may have to stay at least 3 years (i.e. having a set of 6 mandatory courses to take in which 5 have the previous semester's course as a prerequisite).