Masters Degree in CS with Bachelors in Informatics This kind of question gets thrown around quite a bit around here, but I think my current situation has yet to be addressed. I'm currently studying Informatics ("Information") at a school in the midwest (whose national rank is in the high 20's). 

A bit of background - my concentrations are User Experience Design and Data Analytics. My GPA is a 3.6 and I have work experience as a web developer at the university's school of engineering, in a professor's research group, and an internship at a large internet corporation this past summer. I also do freelance and contract web dev work. In sum, much of my work involves front end web dev although I am also proficient in backend/database languages and have written some web scraping programs and done some natural language processing.

I am considering pursuing a master's degree in CS. Though I'm somewhat of a "jack of all trades" currently, further breadth in a more specific topic (AI or NLP for instance) via a master's degree is something that interests me greatly. Considering I  want to apply to very good (top 20) schools, I'm  worried my application may be considered subpar when compared to undergrads who have studied strictly CS, rather than a more HCI-tinged degree like the one I'm currently in. 

Is this a rational thought, and how should I proceed? Should I take a year off before applying and go into the workforce to acquire more desirable CS skills? Should I study certain materials on my own? Or would I already be considered an acceptable applicant with my current academic standing and skills?

Thanks.
Apply.

Pick a couple of schools you'd like to attend, and analyze the program of studies, especially the prerequisites for the courses you find the most tantalizing.  That will show you what course(s) to take in spring and summer, to get you better prepared for your new endeavor!

See Personal statement to apply for graduate school with a change in major