I will be teaching English as a second language for Communications majors next semester and I need a book that deals with the specific vocabulary they need.

Understanding ESL Writers: A Guide For Teachers, by Ilona (I-L-O-N-A) Leki is a very good starting book. It should be available at a local university library and if it's not suitable, Ilona has an excellent bibliography you can draw from.

I would suggest opening an alibris account and collecting an entire raft of material from which to patch together elements of strength from each particular text which serves some but not all of your possible learning needs.

Also, do an audit of online course syllabi at comparable sized colleges or universities to see what is being taught currently.

If you are in an urban area with lots of campus bookstores, take time to see what they are currently using to meet similar needs.

Making Content Comprehensible for English Learners - The SIOP Model - by Jana Echevarria, MaryEllen Vogt, & Deborah J. Short.

We're using it in a master's course I'm taking right now. It may be hard to use the whole SIOP model for what you're doing, but there's a lot of good pointers.