Honestly, if your goal is to become an ASL interpreter, you've got to stay focused. Learn ASL first, then take your ITP courses. If you want to take advanced linguistics courses later in a graduate program, fine. But get the basics under your belt first. Everything else is a distraction and will detour you from your goal.
I've got to agree with Rheba. I am in the thick of the terp program now. My minor is psychology, and advocacy related courses. The saddest thing is that all of these courses are wondeful, but it robs me of time to practice and to attend social events and bonco games,
with my Deaf friends. Hanging out at Deaf events or just a small gathering, or just being with one of your Deaf friends is the best way to increase your vocabulary and skills. That way you can stop a person in conversation and ask for a clarification of a new sign etc.
I was just reading that Shel90 and Jillio had posted, in past posts, that it takes about 5 years to become even a little fluent in ASL. I work very hard at it, and my receptive skills can really suck if the signer is going too fast. Especially finger-spelling. So take this time to immerse yourself in ASL. You can always further your linguistic studies later. You will probably get a bit of linguistic stuff in your second year of ASL anyway. You will study how ASL grows and changes and a lot of cool words that are linguistically related... LOL...
I highly suggest against you veering off yet, but If you just HAVE to know a little more now, check out a book called "Whats Your Sign for Pizza." It discusses the evolution of ASL and how different dialects and cultures affect ASL. I think trying to get through that book will give you a taste of how hard linguistic studies really are. If that isn't enough for you, then look up William Stokie and read some of the exerpts of his linguistic studies and how he put together the ASL dictionary. It will blow you away.
I think that you would be more wise to rely on the advice of your Deaf friends here and Stay true to your goal my friend, and don't set yourself up for failure. One day at a time,, baby steps now,,, and soon you will be running... Before you know it,, your hands will be flying.